# Tabulo [![Gem Version][GV img]][Gem Version] [![Documentation][DC img]][Documentation] [![Coverage Status][CS img]][Coverage Status] [![Build Status][BS img]][Build Status] [![Code Climate][CC img]][Code Climate] [![Awesome][AR img]][Awesome Ruby] Tabulo is a Ruby library for generating plain text tables (also known as “terminal tables” or “ASCII tables”). It is both highly configurable and very easy to use. ## Overview _Quick API:_ ``` > puts Tabulo::Table.new(User.all, :id, :first_name, :last_name).pack +----+------------+-----------+ | id | first_name | last_name | +----+------------+-----------+ | 1 | John | Citizen | | 2 | Jane | Doe | +----+------------+-----------+ ``` _Full API:_ ``` table = Tabulo::Table.new(User.all) do |t| t.add_column("ID", &:id) t.add_column("First name", &:first_name) t.add_column("Last name") { |user| user.last_name.upcase } end ``` ``` > puts table.pack +----+------------+-----------+ | ID | First name | Last name | +----+------------+-----------+ | 1 | John | CITIZEN | | 2 | Jane | DOE | +----+------------+-----------+ ``` ## Features * Presents a [DRY API](#adding-columns) that is column-based, not row-based, meaning header and body rows are automatically in sync * Lets you set [fixed column widths](#fixed-column-widths), then either [wrap](#overflow-handling) or [truncate](#overflow-handling) the overflow * Alternatively, [“pack”](#pack) the table so that columns are auto-sized to their contents, but [without overflowing the terminal](#max-table-width) * Cell alignment is [configurable](#cell-alignment), but has helpful content-based defaults (numbers right, strings left) * Tabulate any `Enumerable`: the underlying collection need not be an array * [Step through](#enumerator) your table a row at a time, printing as you go, without waiting for the underlying collection to load. In other words, have a [streaming interface](#enumerator) for free. * Add an optional [title](#title) to your table * The header row can be [repeated](#repeating-headers) at arbitrary intervals * Newlines within cell content are correctly handled * Multibyte Unicode characters are correctly handled * Apply [colours](#colours-and-styling) and other styling to table content and borders, without breaking the table * Easily [transpose](#transposition) the table, so that rows are swapped with columns * Choose from multiple [border configurations](#borders), including Markdown, “ASCII”, and smoothly joined Unicode border characters Tabulo has also been ported to Crystal (with some modifications): see [Tablo](https://github.com/hutou/tablo). ## Contents * [Overview](#overview) * [Features](#features) * [Table of contents](#table-of-contents) * [Installation](#installation) * [Detailed usage](#detailed-usage) * [Creating a table](#table-initialization) * [Adding columns](#adding-columns) * [Quick API](#quick-api) * [Full API](#quick-api) * [Column labels _vs_ headers](#labels-headers) * [Positioning columns](#column-positioning) * [Removing columns](#removing-columns) * [Adding a title](#title) * [Cell alignment](#cell-alignment) * [Column width, wrapping and truncation](#column-width-wrapping-and-truncation) * [Configuring fixed widths](#configuring-fixed-widths) * [Automating column widths](#automating-column-widths) * [Configuring padding](#configuring-padding) * [Overflow handling](#overflow-handling) * [Manual cell wrapping](#manual-wrapping) * [Formatting cell values](#formatting-cell-values) * [Colours and other styling](#colours-and-styling) * [Styling cell content](#styling-cell-content) * [Styling column headers](#styling-column-headers) * [Styling the table title](#styling-title) * [Setting default styles](#default-styles) * [Styling borders](#styling-borders) * [Repeating headers](#repeating-headers) * [Using a Table Enumerator](#using-a-table-enumerator) * [Accessing cell values](#accessing-cell-values) * [Accessing the underlying enumerable](#accessing-sources) * [Transposing rows and columns](#transposition) * [Border configuration](#borders) * [Row dividers](#dividers) * [Using a table as a snapshot rather than as a dynamic view](#freezing-a-table) * [Comparison with other libraries](#motivation) * [Contributing](#contributing) * [License](#license) ## Installation [↑](#contents) Add this line to your application’s Gemfile: ```ruby gem 'tabulo' ``` And then execute: $ bundle Or install it yourself: $ gem install tabulo To use the gem, you need to require it in your source code as follows: ```ruby require 'tabulo' ``` ### Creating a table [↑](#contents) You instantiate a `Tabulo::Table` by passing it an underlying `Enumerable`, being the collection of things that you want to tabulate. Each member of this collection will end up corresponding to a row of the table. The collection can be any `Enumerable`, for example a Ruby `Array`, or an ActiveRecord relation: ```ruby table = Tabulo::Table.new([1, 2, 5]) other_table = Tabulo::Table.new(User.all) ``` For the table to be useful, however, it must also contain columns… ### Adding columns [↑](#contents) #### Quick API [↑](#contents) When the columns correspond to methods on members of the underlying enumerable, you can use the “quick API”, by passing a symbol directly to `Tabulo::Table.new` for each column. This symbol also provides the column header: ```ruby table = Tabulo::Table.new([1, 2, 5], :itself, :even?, :odd?) ``` ``` > puts table +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 5 | false | true | +--------------+--------------+--------------+ ``` #### Full API [↑](#contents) Columns can also be added to the table one-by-one using `add_column`. This “full API” is more verbose, but provides greater configurability: ```ruby table = Tabulo::Table.new([1, 2, 5]) table.add_column(:itself) table.add_column(:even?) table.add_column(:odd?) ``` Alternatively, you can pass an initialization block to `new`: ```ruby table = Tabulo::Table.new([1, 2, 5]) do |t| t.add_column(:itself) t.add_column(:even?) t.add_column(:odd?) end ``` With the full API, columns can also be initialized using a callable to which each object will be passed to determine the value to be displayed in the table. In this case, the first argument to `add_column` provides the header text: ```ruby table = Tabulo::Table.new([1, 2, 5]) do |t| t.add_column("N", &:itself) t.add_column("Doubled") { |n| n * 2 } t.add_column(:odd?) end ``` ``` > puts table +--------------+--------------+--------------+ | N | Doubled | odd? | +--------------+--------------+--------------+ | 1 | 2 | true | | 2 | 4 | false | | 5 | 10 | true | +--------------+--------------+--------------+ ``` The `add_column` method can be passed a single parameter callable, as shown in the above example, with the parameter representing the member of the underyling enumerable; or it can be passed 2-parameter callable, with the second parameter representing the (0-based) index of each row. This can be useful if you want to display a row number in one of the columns: ```ruby table = Tabulo::Table.new(["a", "b", "c"]) do |t| t.add_column("Row") { |letter, row_index| row_index } t.add_column("Value", &:itself) end ``` ``` > puts table +--------------+--------------+ | Row | Value | +--------------+--------------+ | 0 | a | | 1 | b | | 2 | c | +--------------+--------------+ ``` #### Column labels _vs_ headers [↑](#contents) The first argument to `add_column` is the called the _label_ for that column. It serves as the column’s unique identifier: only one column may have a given label per table. (`String`s and `Symbol`s are interchangeable for this purpose.) The label also forms the header shown at the top of the column, unless a separate `header:` argument is explicitly passed: ```ruby table.add_column(:itself, header: "N") table.add_column(:itself2, header: "N", &:itself) # header need not be unique # table.add_column(:itself) # would raise Tabulo::InvalidColumnLabelError, as label must be unique ``` #### Positioning columns [↑](#contents) By default, each new column is added to the right of all the other columns so far added to the table. However, if you want to insert a new column into some other position, you can use the `before` option, passing the label of the column to the left of which you want the new column to be added: ```ruby table = Tabulo::Table.new([1, 2, 3], :itself, :odd?) table.add_column(:even?, before: :odd?) ``` ``` > puts table +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 5 | false | true | +--------------+--------------+--------------+ ``` ### Removing columns [↑](#contents) There is also a `#remove_column` method, for deleting an existing column from a table. Pass it the label of the column you want to remove: ```ruby table.remove_column(:even?) ``` ### Adding a title [↑](#contents) You can give your table a title, using the `title` option: ```ruby table = Tabulo::Table.new([1, 2, 3], :itself, :even?, :odd?, title: "Numbers") ``` ``` > puts table +--------------------------------------------+ | Numbers | +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | +--------------+--------------+--------------+ ``` There is a caveat: Using the `title` option with the `:markdown` [border type](#borders) will cause the rendered table to cease being valid Markdown, as unfortunately almost no markdown engines support adding a captions (i.e. titles) to tables. ### Cell alignment [↑](#contents) By default, column header text is center-aligned, while the content of each body cell is aligned according to its data type. Numbers are right-aligned, text is left-aligned, and booleans (`false` and `true`) are center-aligned. This default behaviour can be set at the table level, by passing `:center`, `:left` or `:right` to the `align_header` or `align_body` options when initializing the table: ```ruby table = Tabulo::Table.new([1, 2], :itself, :even?, align_header: :left, align_body: :right) ``` The table-level alignment settings can be overridden for individual columns by passing similarly-named options to `add_column`, e.g.: ```ruby table.add_column("Doubled", align_header: :right, align_body: :left) { |n| n * 2 } ``` If a table title is present, it is center-aligned by default. This can be changed using the `align_title` option when initializing the table: ```ruby table = Tabulo::Table.new([1, 2], :itself, :even?, title: "Numbers", align_title: :left) ``` ### Column width, wrapping and truncation [↑](#contents) #### Configuring fixed widths [↑](#contents) By default, column width is fixed at 12 characters, plus 1 character of padding on either side. This can be adjusted on a column-by-column basis using the `width` option of `add_column`: ```ruby table = Tabulo::Table.new([1, 2]) do |t| t.add_column(:itself, width: 6) t.add_column(:even?, width: 9) end ``` ``` > puts table +--------+-----------+ | itself | even? | +--------+-----------+ | 1 | false | | 2 | true | +--------+-----------+ ``` If you want to set the default column width for all columns of the table to something other than 12, use the `column_width` option when initializing the table: ```ruby table = Tabulo::Table.new([1, 2], :itself, :even?, column_width: 6) ``` ``` > puts table +--------+--------+ | itself | even? | +--------+--------+ | 1 | false | | 2 | true | +--------+--------+ ``` Widths set for individual columns always override the default column width for the table. #### Automating column widths [↑](#contents) Instead of setting column widths “manually”, you can tell the table to sort out the widths itself, so that each column is just wide enough for its header and contents (plus a character of padding on either side): ```ruby table = Tabulo::Table.new(["short", "here is a longer phrase"], :itself, :size) table.pack ``` ``` > puts table +-------------------------+------+ | itself | size | +-------------------------+------+ | short | 5 | | here is a longer phrase | 23 | +-------------------------+------+ ``` If the table [title](#title) happens to be too long to for the existing width of the table, `pack` will also arrange for the table to be widened sufficiently to accommodate it without wrapping: ```ruby table = Tabulo::Table.new(["a", "b"], :itself, :size, title: "Here are some letters of the alphabet") table.pack ``` ``` > puts table +---------------------------------------+ | Here are some letters of the alphabet | +-------------------+-------------------+ | itself | size | +-------------------+-------------------+ | a | 1 | | b | 1 | +-------------------+-------------------+ ``` The `pack` method returns the table itself, so you can “pack-and-print” in one go: ```ruby puts Tabulo::Table.new(["short", "here is a longer phrase"], :itself, :size).pack ``` You can manually place an upper limit on the total width of the table when packing: ```ruby puts Tabulo::Table.new(["short", "here is a longer phrase"], :itself, :size).pack(max_table_width: 24) ``` ``` +---------------+------+ | itself | size | +---------------+------+ | short | 5 | | here is a lon | 23 | | ger phrase | | +---------------+------+ ``` Or if you simply call `pack` with no arguments (or if you explicitly call `pack(max_table_width: :auto)`), the table width will automatically be capped at the width of your terminal. If you want the table width not to be capped at all, call `pack(max_table_width: nil)`. If the table cannot be fit within the width of the terminal, or the specified maximum width, then column widths are reduced as required, with wrapping or truncation then occuring as necessary (see [Overflow handling](#overflow-handling)). Under the hood, a character of width is deducted column by column—the widest column being targetted each time—until the table will fit. Note that `pack`ing the table necessarily involves traversing the entire collection up front as the maximum cell width needs to be calculated for each column. You may not want to do this if the collection is very large. Note also the effect of `pack` is to fix the column widths as appropriate to the formatted cell contents given the state of the underlying collection _at the point of packing_. If the underlying collection changes between that point, and when the table is printed, then the columns will _not_ be resized yet again on printing. This is a consequence of the table always being essentially a “live view” on the underlying collection: formatted contents are never cached within the table itself. There are [ways around this](#freezing-a-table), however, if this is not the desired behaviour—see [below](#freezing-a-table). #### Configuring padding [↑](#contents) The single character of padding either side of each column is not counted in the column width. The amount of this extra padding can be configured for the table as a whole, using the `column_padding` option passed to `Table.new`—the default value of this option being `1`. Passing a single integer to this option causes the given amount of padding to be applied to each side of each column. For example: ```ruby table = Tabulo::Table.new([1, 2, 5], :itself, :even?, :odd?, column_padding: 0) ``` ``` > puts table.pack +------+-----+-----+ |itself|even?| odd?| +------+-----+-----+ | 1|false| true| | 2| true|false| | 5|false| true| +------+-----+-----+ ``` Passing an array of _two_ integers to this option configures the left and right padding for each column, according to the first and second element of the array, respectively. For example: ```ruby table = Tabulo::Table.new([1, 2, 5], :itself, :even?, :odd?, column_padding: [0, 2]) ``` ``` > puts table.pack +--------+-------+-------+ |itself |even? | odd? | +--------+-------+-------+ | 1 |false | true | | 2 | true |false | | 5 |false | true | +--------+-------+-------+ ``` Note how the padding amount is completely unaffected by the call `pack`. Padding can also be configured on a column-by-column basis, using the `padding` option when calling `add_column`: ```ruby table = Tabulo::Table.new([1, 2, 5], :itself, :even?) table.add_column(:odd?, padding: 3) ``` ``` > puts table.pack +--------+-------+-----------+ | itself | even? | odd? | +--------+-------+-----------+ | 1 | false | true | | 2 | true | false | | 5 | false | true | +--------+-------+-----------+ ``` This column-level `padding` setting always overrides any table-level `column_padding` setting, for the column in question. #### Overflow handling [↑](#contents) By default, if cell contents exceed their column width, they are wrapped for as many rows as required: ```ruby table = Tabulo::Table.new( ["hello", "abcdefghijklmnopqrstuvwxyz"], :itself, :length ) ``` ``` > puts table +--------------+--------------+ | itself | length | +--------------+--------------+ | hello | 5 | | abcdefghijkl | 26 | | mnopqrstuvwx | | | yz | | +--------------+--------------+ ``` Wrapping behaviour is configured for the table as a whole using the `wrap_header_cells_to` option for header cells and `wrap_body_cells_to` for body cells, both of which default to `nil`, meaning that cells are wrapped to as many rows as required. Passing an `Integer` limits wrapping to the given number of rows, with content truncated from that point on. The `~` character is appended to the outputted cell content to show that truncation has occurred: ```ruby table = Tabulo::Table.new( ["hello", "abcdefghijklmnopqrstuvwxyz"], :itself, :length, wrap_body_cells_to: 1 ) ``` ``` > puts table +--------------+--------------+ | itself | length | +--------------+--------------+ | hello | 5 | | abcdefghijkl~| 26 | +--------------+--------------+ ``` The character used to indicate truncation, which defaults to `~`, can be configured using the `truncation_indicator` option passed to `Table.new`. #### Manual cell wrapping [↑](#contents) You can “manually” wrap the content of a title, header or body cell at a particular point, simply by placing a newline character, at that point: ```ruby table = Tabulo::Table.new(1..3) do |t| t.add_column("The number\nitself", &:itself) t.add_column("Even?", &:even?) t.add_column("Odd?", &:odd?) end ``` ``` > puts table +--------------+--------------+--------------+ | The number | Even? | Odd? | | itself | | | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | +--------------+--------------+--------------+ ``` Tabulo will treat any of the character combinations `"\n"`, `"\r\n"` or `"\r"` equally, as a line break, regardless of the platform it’s currently being run on. This ensures things are formatted as expected if, for example, you are examining content that was produced on another platform from the one you’re running Tabulo on. ### Formatting cell values [↑](#contents) While the callable passed to `add_column` determines the underyling, calculated value in each cell of the column, there is a separate concept, of a “formatter”, that determines how that value will be visually displayed. By default, `.to_s` is called on the underlying cell value to “format” it; however, you can format it differently by passing another callable to the `formatter` option of `add_column`: ```ruby table = Tabulo::Table.new(1..3) do |t| t.add_column("N", &:itself) t.add_column("Reciprocal", formatter: -> (n) { "%.2f" % n }) do |n| 1.0 / n end end ``` ``` > puts table +--------------+--------------+ | N | Reciprocal | +--------------+--------------+ | 1 | 1.00 | | 2 | 0.50 | | 3 | 0.33 | +--------------+--------------+ ``` Note the numbers in the “Reciprocal” column in this example are still right-aligned, even though the callable passed to `formatter` returns a String. Default cell alignment is determined by the type of the underlying cell value, not the way it is formatted. This is usually the desired result. If you want to set the default formatter for all columns of the table to something other than `#to_s`, use the `formatter` option when initializing the table: ```ruby table = Tabulo::Table.new(1..3, formatter: -> (n) { "%.2f" % n }) do |t| t.add_column("N", &:itself) t.add_column("Reciprocal") { |n| 1.0 / n } t.add_column("Half") { |n| n / 2.0 } end ``` ``` > puts table +--------------+--------------+--------------+ | N | Reciprocal | Half | +--------------+--------------+--------------+ | 1.00 | 1.00 | 0.50 | | 2.00 | 0.50 | 1.00 | | 3.00 | 0.33 | 1.50 | +--------------+--------------+--------------+ ``` Formatters set for individual columns on calling `#add_column` always override the default formatter for the table. The `formatter` callback also has an alternative, 2-parameter version. If `formatter` is passed a 2-parameter callable, the second parameter will be given a `CellData` instance, containing additional information about the cell that may be useful in determining how to format it—see the [documentation](https://www.rubydoc.info/gems/tabulo/2.6.2/Tabulo/CellData.html) for details. ### Colours and other styling [↑](#contents) #### Styling cell content [↑](#contents) In most terminals, if you want to print text that is coloured, or has certain other styles such as underlining, you need to use ANSI escape sequences, either directly, or by means of a library such as [Rainbow](http://github.com/sickill/rainbow) that uses them internally. Tabulo needs to properly account for escape sequences when performing the width calculations required to render tables. The `styler` option on the `add_column` method is intended to facilitate this. For example, suppose you have a table to which you want to add a column that displays `true` in green if a given number is even, or else displays `false` in red. You can achieve this as follows using raw ANSI escape codes: ```ruby table.add_column( :even?, styler: -> (cell_value, s) { cell_value ? "\033[32m#{s}\033[0m" : "\033[31m#{s}\033[0m" } ) ``` Or, if you are using the [rainbow](https://github.com/sickill/rainbow) gem for colouring, you could do the following: ```ruby require "rainbow" # ... table.add_column( :even?, styler: -> (cell_value, s) { cell_value ? Rainbow(s).green : Rainbow(s).red } ) ``` The `styler` option should be passed a callable that takes either 2, 3 or 4 parameters. The first parameter represents the underlying value of the cell (in this case a boolean indicating whether the number is even). The second parameter represents the formatted string value of that cell, i.e. the cell content after any processing by the [formatter](#formatting-cell-values). The third and fourth parameters are optional, and contain further information about the cell and its contents that may be useful in determining how to style it. See the [documentation](https://www.rubydoc.info/gems/tabulo/2.6.2/Tabulo/Table#add_column-instance_method) for details. If the content of a cell is wrapped over multiple lines, then the `styler` will be called once per line, so that each line of the cell will have the escape sequence applied to it separately (ensuring the styling doesn’t bleed into neighbouring cells). If the content of a cell has been [truncated](#overflow-handling), then whatever colours or other styling apply to the cell content will also be applied the truncation indicator character. #### Styling column headers [↑](#contents) If you want to apply colours or other styling to the content of a column header, as opposed to cells in the table body, use the `header_styler` option, e.g.: ```ruby table.add_column(:even?, header_styler: -> (s) { "\033[32m#{s}\033[0m" }) ``` The `header_styler` option accepts a 1-, 2- or 3-parameter callable. See the [documentation](https://www.rubydoc.info/gems/tabulo/2.6.2/Tabulo/Table#add_column-instance_method) for details. #### Styling the table title [↑](#contents) To apply colours or other styling to the table title, if present, use the `title_styler` option when initializing the table. This accepts a single-parameter callable: ```ruby table = Tabulo::Table.new(1..5, :itself, :even?, :odd?, title: "Numbers", title_styler: -> (s) { "\033[32m#{s}\033[0m" }) ``` The `title_styler` option accepts a 1- or 2-parameter callable. See the [documentation](https://www.rubydoc.info/gems/tabulo/2.6.2/Tabulo/Table#initialize-instance_method) for details. #### Styling borders [↑](#contents) Styling can also be applied to borders and dividing lines, using the `border_styler` option when initializing the table, e.g.: ```ruby table = Tabulo::Table.new(1..5, :itself, :even?, :odd?, border_styler: -> (s) { "\033[32m#{s}\033[0m" }) ``` #### Setting default styles [↑](#contents) By default, no styling is applied to the headers or body content of a column unless configured to do so via the `header_styler` or `styler` option when calling `add_column` for that particular column. It is possible to apply styling by default to _all_ columns in a table, however, as the table initializer also accepts both a `header_styler` and a `styler` option. For example, if you want all the header text in the table to be green, you could do: ```ruby table = Tabulo::Table.new(1..5, :itself, :even?, :odd?, header_styler: -> (s) { "\033[32m#{s}\033[0m" }) ``` Now, all columns in the table will automatically have green header text, unless overridden by another header styler being passed to `#add_column`. ### Repeating headers [↑](#contents) By default, headers are only shown once, at the top of the table (`header_frequency: :start`). If `header_frequency` is passed `nil`, headers are not shown at all; or, if passed an `Integer` N, headers are shown at the top and then repeated every N rows. This can be handy when you’re looking at table that’s taller than your terminal. E.g.: ```ruby table = Tabulo::Table.new(1..10, :itself, :even?, header_frequency: 5) ``` ``` > puts table +--------------+--------------+ | itself | even? | +--------------+--------------+ | 1 | false | | 2 | true | | 3 | false | | 4 | true | | 5 | false | +--------------+--------------+ | itself | even? | +--------------+--------------+ | 6 | true | | 7 | false | | 8 | true | | 9 | false | | 10 | true | +--------------+--------------+ ``` Note that if the table has a [title](#title), it will not be repeated; only column headers are repeated. ### Using a Table Enumerator [↑](#contents) Because it’s an `Enumerable`, a `Tabulo::Table` can also give you an `Enumerator`, which is useful when you want to step through rows one at a time. In a Rails console, for example, you might do this: ``` > e = Tabulo::Table.new(User.find_each) do |t| t.add_column(:id) t.add_column(:email, width: 24) end.to_enum # <-- make an Enumerator ... > puts e.next +--------------+--------------------------+ | id | email | +--------------+--------------------------+ | 1 | jane@example.com | => nil > puts e.next | 2 | betty@example.net | => nil ``` Note the use of `.find_each`: we can start printing the table without having to load the entire underlying collection. (This is negated if we [pack](#pack) the table, however, since in that case the entire collection must be traversed up front in order for column widths to be calculated.) ### Accessing cell values [↑](#contents) Each `Tabulo::Table` is an `Enumerable` of which each element is a `Tabulo::Row`. Each `Tabulo::Row` is itself an `Enumerable`, of `Tabulo::Cell`. The `Tabulo::Cell#value` method will return the underlying value of the cell; while `Tabulo::Cell#formatted_content` will return its formatted content as a string. A `Tabulo::Row` can also be converted to a `Hash` for keyed access. For example: ```ruby table = Tabulo::Table.new(1..3, :itself, :even?, :odd?) table.each do |row| row.each { |cell| puts cell.value } # 1, false, true...2, true, false...3, false, true puts row.to_h[:even?].value # false...true...false end ``` The column label (being the first argument that was passed to `add_column`, converted if necessary to a `Symbol`), always forms the key for the purposes of this `Hash`: ```ruby table = Tabulo::Table.new(1..3) do |t| t.add_column("Number") { |n| n } t.add_column(:doubled, header: "Number X 2") { |n| n * 2 } end table.each do |row| cells = row.to_h puts cells[:Number].value # 1...2...3... puts cells[:doubled].value # 2...4...6... end ``` ### Accessing the underlying enumerable [↑](#contents) The underlying enumerable for a table can be retrieved by calling the `sources` getter: ```ruby table = Tabulo::Table.new([1, 2, 5], :itself, :even?, :odd?) ``` ``` > table.sources => [1, 2, 5] ``` There is also a corresponding setter, meaning you can reuse the same table to tabulate a different data set, without having to reconfigure the columns and other options from scratch: ```ruby table.sources = [50, 60] ``` ``` > table.sources => [50, 60] ``` In addition, the element of the underlying enumerable corresponding to a particular row can be accessed by calling the `source` method on that row: ```ruby table.each do |row| puts row.source # 50...60... end ``` ### Transposing rows and columns [↑](#contents) By default, Tabulo generates a table in which each row corresponds to a _record_, i.e. an element of the underlying enumerable, and each column to a _field_. However, there are times when one instead wants each row to represent a field, and each column a record. This is generally the case when there are a small number or records but a large number of fields. To produce such a table, we can first initialize an ordinary table, specifying fields as columns, and then call `transpose`, which returns a new table in which the rows and columns are swapped: ```ruby > puts Tabulo::Table.new(-1..1, :even?, :odd?, :zero?, :pred, :succ, :abs).transpose ``` ``` +-------+--------------+--------------+--------------+ | | -1 | 0 | 1 | +-------+--------------+--------------+--------------+ | even? | false | true | false | | odd? | true | false | true | | zero? | false | true | false | | pred | -2 | -1 | 0 | | succ | 0 | 1 | 2 | | abs | 1 | 0 | 1 | +-------+--------------+--------------+--------------+ ``` By default, a header row is added to the new table, showing the string value of the element represented in that column. This can be configured, however, along with other aspects of `transpose`’s behaviour. For details, see the [documentation](https://www.rubydoc.info/gems/tabulo/2.6.2/Tabulo/Table#transpose-instance_method). ### Configuring borders [↑](#contents) You can configure the kind of border and divider characters that are used when the table is printed. This is done using the `border` option passed to `Table.new`. The options are as follows. `:ascii`—this is the default; the table is drawn entirely with characters in the ASCII set: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :ascii) +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | +--------------+--------------+--------------+ > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :ascii, title: "Numbers") +--------------------------------------------+ | Numbers | +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | +--------------+--------------+--------------+ ``` `:modern`—uses smoothly joined Unicode characters: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :modern) ┌──────────────┬──────────────┬──────────────┐ │ itself │ even? │ odd? │ ├──────────────┼──────────────┼──────────────┤ │ 1 │ false │ true │ │ 2 │ true │ false │ │ 3 │ false │ true │ └──────────────┴──────────────┴──────────────┘ > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :modern, title: "Numbers") ┌────────────────────────────────────────────┐ │ Numbers │ ├──────────────┬──────────────┬──────────────┤ │ itself │ even? │ odd? │ ├──────────────┼──────────────┼──────────────┤ │ 1 │ false │ true │ │ 2 │ true │ false │ │ 3 │ false │ true │ └──────────────┴──────────────┴──────────────┘ ``` _Note: The unicode characters used for the `:modern` border may not render properly when viewing this documentation on some browsers or devices. This doesn’t reflect any brokenness in `tabulo` itself._ `:markdown`—renders a GitHub flavoured Markdown table: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :markdown) | itself | even? | odd? | |--------------|--------------|--------------| | 1 | false | true | | 2 | true | false | | 3 | false | true | > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :markdown, title: "Numbers") | Numbers | | itself | even? | odd? | |--------------|--------------|--------------| | 1 | false | true | | 2 | true | false | | 3 | false | true | ``` _However_, note that when a table is rendered using the `:markdown` border type in combination with a (non-`nil`) `title`, the result will be _invalid Markdown_. This is because Markdown engines do not generally support adding a caption (i.e. title) element to tables. `:blank`—no border or divider characters are printed: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :blank) itself even? odd? 1 false true 2 true false 3 false true > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :blank, title: "Numbers") Numbers itself even? odd? 1 false true 2 true false 3 false true ``` `:reduced_ascii`—similar to `:ascii`, but without vertical lines: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :reduced_modern) -------------- -------------- -------------- itself even? odd? -------------- -------------- -------------- 1 false true 2 true false 3 false true -------------- -------------- -------------- > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :reduced_modern, title: "Numbers") -------------------------------------------- Numbers -------------- -------------- -------------- itself even? odd? -------------- -------------- -------------- 1 false true 2 true false 3 false true -------------- -------------- -------------- ``` `:reduced_modern`—similar to `:modern`, but without vertical lines: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :reduced_ascii) ────────────── ────────────── ────────────── itself even? odd? ────────────── ────────────── ────────────── 1 false true 2 true false 3 false true ────────────── ────────────── ────────────── > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :reduced_ascii, title: "Numbers") ──────────────────────────────────────────── Numbers ────────────── ────────────── ────────────── itself even? odd? ────────────── ────────────── ────────────── 1 false true 2 true false 3 false true ────────────── ────────────── ────────────── ``` _Note: The unicode characters used for the `:reduced_modern` border may not render properly when viewing this documentation on some browsers or devices. This doesn’t reflect any brokenness in `tabulo` itself._ `:classic`—reproduces the default behaviour in Tabulo v1; this is like the `:ascii` option, but without a bottom border: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :classic) +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, border: :classic, title: "Numbers") +--------------------------------------------+ | Numbers | +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | ``` Note that, by default, none of the border options includes lines drawn _between_ rows in the body of the table. These are configured via a separate option: see [below](#dividers). ### Row dividers [↑](#contents) To add lines between rows in the table body, use the `row_divider_frequency` option when initializing the table. The default value for this option is `nil`, meaning there are no dividing lines between rows. But if this option passed is a positive integer N, then a dividing line is inserted before every Nth row. For example: ``` > puts Tabulo::Table.new(1..6, :itself, :even?, :odd?, row_divider_frequency: 2) +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | +--------------+--------------+--------------+ | 3 | false | true | | 4 | true | false | +--------------+--------------+--------------+ | 5 | false | true | | 6 | true | false | +--------------+--------------+--------------+ ``` If you want a line before every row, pass `1` to `row_divider_frequency`. For example: ``` > puts Tabulo::Table.new(1..3, :itself, :even?, :odd?, row_divider_frequency: 1) +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | +--------------+--------------+--------------+ | 2 | true | false | +--------------+--------------+--------------+ | 3 | false | true | +--------------+--------------+--------------+ ``` ### Using a table as a snapshot rather than as a dynamic view [↑](#contents) The nature of a `Tabulo::Table` is that of a dynamic view onto the underlying `sources` enumerable from which it was initialized (or which was subsequently assigned to its `sources` attribute). That is, if the contents of the `sources` enumerable change subsequent to initialization of or assignment to `sources`, then the table when printed will show the `sources` as they are at the time of printing, not as they were at the time of initialization or assignment. For example: ```ruby arr = [1, 2] table = Tabulo::Table.new(arr, :itself, :even?, :odd?) ``` ``` > puts table +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | +--------------+--------------+--------------+ ``` ```ruby arr << 3 ``` ``` > puts table +--------------+--------------+--------------+ | itself | even? | odd? | +--------------+--------------+--------------+ | 1 | false | true | | 2 | true | false | | 3 | false | true | +--------------+--------------+--------------+ ``` In this example, even though no direct mutations have been made to `table`, the result of calling `puts table` has changed, in virtue of a mutation on the underyling enumerable `arr`. A similar behaviour can be seen when `sources` is an ActiveRecord query, and there are changes to the relevant database table(s) such that the result of the query changes. This is worth bearing in mind when calling [`pack`](#pack) on a table, since if the `sources` enumerable changes between `pack`ing and printing, then the column widths calculated by the `pack` method may no longer be “just right” given the changed `sources`. If this is not the desired behaviour, there are ways around this. For example, if dealing with an ActiveRecord relation, you can convert the query to a plain array before initializing the table: ```ruby sources = User.all.to_a table = Tabulo::Table.new(sources, :id, :first_name, :last_name) table.pack puts table ``` Passing an `Array` rather than the ActiveRecord query directly means that if there are changes to the content of the `users` database table, these will not be reflected in the rendered content of the `Tabulo::Table` (unless some of the `Tabulo::Table` columns are based on callables that perform further database queries when called…). Note that it is also possible simply to store the string value of a table for later use, rather than the table itself: ```ruby rendered_table = Tabulo::Table.new(1..10, :itself, :even?, :odd?).pack.to_s ``` ## Comparison with other libraries [↑](#contents) There are other libraries for generating plain text tables in Ruby. Popular among these are: * [terminal-table](https://github.com/tj/terminal-table) * [tty-table](https://github.com/piotrmurach/tty-table) * [table\_print](https://github.com/arches/table_print) * [hirb](https://github.com/cldwalker/hirb) *DISCLAIMER: My comments regarding these other libraries are based only on my own, possibly flawed reading of the documentation for, and experimentation with, these libraries at the time of my writing this. Their APIs, features or documentation may well change between when I write this, and when you read it. Please consult the libraries’ own documentation for yourself, rather than relying on these comments.* While these libraries have their strengths, I have personally found that, for the common use case of printing a table on the basis of some underlying enumerable collection (such as an ActiveRecord query result), using these libraries feels more cumbersome than it could be. For example, suppose we have called `User.all` from the Rails console, and want to print a table showing the email, first name, last name and ID of each user, with column headings. Also, we want the ID column to be right-aligned, because it’s a number. In **terminal-table**, we could achieve this as follows: ```ruby rows = User.all.map { |u| [u.email, u.first_name, u.last_name, u.id] } headings = ["email", "first name", "last name", "id"] table = Terminal::Table.new(headings: headings, rows: rows) table.align_column(3, :right) puts table ``` The problem here is that there is no single source of knowledge about which columns appear, and in which order. If we want to add another column to the left of “email”, we need to amend the rows array, and the headings array, and the index passed to `align_column`. We bear the burden of keeping these three in sync. This is not be a big deal for small one-off tables, but for tables that have many columns, or that are constructed dynamically based on user input or other runtime factors determining the columns to be included, this can be a hassle and a source of brittleness. **tty-table** has a somewhat different API to `terminal-table`. It offers both a “row-based” and a “column-based” method of initializing a table. The row-based method is similar to `terminal-table`’s in that it burdens the developer with syncing the column ordering across multiple code locations. The “column-based” API for `tty-table`, on the other hand, seems to avoid this problem. One way of using it is like this: ```ruby users = User.all table = TTY::Table.new [ { "email" => users.map(&:email), "first name" => users.map(&:first_name), "last name" => users.map(&:last_name), "id" => users.map(&:id), } ] puts table ``` While this doesn’t seem too bad, it does mean that the underlying collection (`users`) has to be traversed multiple times, once for each column, which is inefficient, particularly if the underlying collection is large. In addition, it’s not clear how to pass separate formatting information for each column when initializing in this way. (Perhaps there is a way to do this, but if there is, it doesn’t seem to be documented.) So it seems we still have to use `table.align_column(3, :right)`, which again burdens us with keeping the column index passed to `align_column` in sync. As for **table\_print**, this is a handy gem for quickly tabulating ActiveRecord collections from the Rails console. `table_print` is similar to `tabulo` in that it has a column-based API, so it doesn’t suffer from the multiple-source-of-knowledge issue in regards to column orderings. However, it lacks certain other useful features, such as the ability to repeat headers every N rows, the automatic alignment of columns based on cell content (numbers right, strings left), and a quick and easy way to automatically resize columns to accommodate cell content without overflowing the terminal. Also, as of the time of writing, `table_print`’s last significant commit (ignoring a deprecation warning fix in April 2018) was in March 2016. Finally, it is worth mentioning the **hirb** library. This is similar to `table_print`, in that it’s well suited to quickly displaying ActiveRecord collections from the Rails console. However, like `table_print`, there are certain useful features it’s lacking; and using it outside the console environment seems cumbersome. Moreover, it seems no longer to be maintained. At the time of writing, its last commit was in March 2015. ## Contributing [↑](#contents) Issues and pull requests are welcome on GitHub at https://github.com/matt-harvey/tabulo. To start working on Tabulo, `git clone` and `cd` into your fork of the repo, then run `bin/setup` to install dependencies. `bin/console` will give you an interactive prompt that will allow you to experiment; and `bundle exec rake spec` will run the test suite. For a list of other Rake tasks that are available in the development environment, run `bundle exec rake -T`. ## License [↑](#contents) The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT). 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