# Amoeba Easy cloning of active_record objects including associations and several operations under associations and attributes. [![Maintainability](https://api.codeclimate.com/v1/badges/d4809ae57ca999fff022/maintainability)](https://codeclimate.com/github/amoeba-rb/amoeba/maintainability) [![Gem Version](https://badge.fury.io/rb/amoeba.svg)](http://badge.fury.io/rb/amoeba) [![Build Status](https://travis-ci.org/amoeba-rb/amoeba.svg?branch=master)](https://travis-ci.org/amoeba-rb/amoeba) ## What? The goal was to be able to easily and quickly reproduce ActiveRecord objects including their children, for example copying a blog post maintaining its associated tags or categories. This gem is named "Amoeba" because amoebas are (small life forms that are) good at reproducing. Their children and grandchildren also reproduce themselves quickly and easily. ### Technical Details An ActiveRecord extension gem to allow the duplication of associated child record objects when duplicating an active record model. Rails 4.x, 5.0, 5.1, 5.2, 6.0, 6.1 compatible. ### Features - Supports the following association types - `has_many` - `has_one :through` - `has_many :through` - `has_and_belongs_to_many` - A simple DSL for configuration of which fields to copy. The DSL can be applied to your rails models or used on the fly. - Supports STI (Single Table Inheritance) children inheriting their parent amoeba settings. - Multiple configuration styles such as inclusive, exclusive and indiscriminate (aka copy everything). - Supports cloning of the children of Many-to-Many records or merely maintaining original associations - Supports automatic drill-down i.e. recursive copying of child and grandchild records. - Supports preprocessing of fields to help indicate uniqueness and ensure the integrity of your data depending on your business logic needs, e.g. prepending "Copy of " or similar text. - Supports preprocessing of fields with custom lambda blocks so you can do basically whatever you want if, for example, you need some custom logic while making copies. - Amoeba can perform the following preprocessing operations on fields of copied records - set - prepend - append - nullify - customize - regex ## Usage ### Installation is hopefully as you would expect: ```sh gem install amoeba ``` or just add it to your Gemfile: ```sh gem 'amoeba' ``` Configure your models with one of the styles below and then just run the `amoeba_dup` method on your model where you would run the `dup` method normally: ```ruby p = Post.create(:title => "Hello World!", :content => "Lorum ipsum dolor") p.comments.create(:content => "I love it!") p.comments.create(:content => "This sucks!") puts Comment.all.count # should be 2 my_copy = p.amoeba_dup my_copy.save puts Comment.all.count # should be 4 ``` By default, when enabled, amoeba will copy any and all associated child records automatically and associate them with the new parent record. You can configure the behavior to only include fields that you list or to only include fields that you don't exclude. Of the three, the most performant will be the indiscriminate style, followed by the inclusive style, and the exclusive style will be the slowest because of the need for an extra explicit check on each field. This performance difference is likely negligible enough that you can choose the style to use based on which is easiest to read and write, however, if your data tree is large enough and you need control over what fields get copied, inclusive style is probably a better choice than exclusive style. ### Configuration Please note that these examples are only loose approximations of real world scenarios and may not be particularly realistic, they are only for the purpose of demonstrating feature usage. #### Indiscriminate Style This is the most basic usage case and will simply enable the copying of any known associations. If you have some models for a blog about like this: ```ruby class Post < ActiveRecord::Base has_many :comments end class Comment < ActiveRecord::Base belongs_to :post end ``` simply add the amoeba configuration block to your model and call the enable method to enable the copying of child records, like this: ```ruby class Post < ActiveRecord::Base has_many :comments amoeba do enable end end class Comment < ActiveRecord::Base belongs_to :post end ``` Child records will be automatically copied when you run the `amoeba_dup` method. #### Inclusive Style If you only want some of the associations copied but not others, you may use the inclusive style: ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags has_many :authors amoeba do enable include_association :tags include_association :authors end end class Comment < ActiveRecord::Base belongs_to :post end ``` Using the inclusive style within the amoeba block actually implies that you wish to enable amoeba, so there is no need to run the enable method, though it won't hurt either: ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags has_many :authors amoeba do include_association :tags include_association :authors end end class Comment < ActiveRecord::Base belongs_to :post end ``` You may also specify fields to be copied by passing an array. If you call the `include_association` with a single value, it will be appended to the list of already included fields. If you pass an array, your array will overwrite the original values. ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags has_many :authors amoeba do include_association [:tags, :authors] end end class Comment < ActiveRecord::Base belongs_to :post end ``` These examples will copy the post's tags and authors but not its comments. The inclusive style, when used, will automatically disable any other style that was previously selected. #### Exclusive Style If you have more fields to include than to exclude, you may wish to shorten the amount of typing and reading you need to do by using the exclusive style. All fields that are not explicitly excluded will be copied: ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags has_many :authors amoeba do exclude_association :comments end end class Comment < ActiveRecord::Base belongs_to :post end ``` This example does the same thing as the inclusive style example, it will copy the post's tags and authors but not its comments. As with inclusive style, there is no need to explicitly enable amoeba when specifying fields to exclude. The exclusive style, when used, will automatically disable any other style that was previously selected, so if you selected include fields, and then you choose some exclude fields, the `exclude_association` method will disable the previously selected inclusive style and wipe out any corresponding include fields. #### Conditions Also if you need to path extra condition for include or exclude relationship you can path method name to `:if` option. ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags amoeba do include_association :comments, if: :popular? end def popular? likes > 15 end end ``` After call `Post.first.amoeba_dup` if `likes` is larger 15 than all comments will be duplicated too, but in another situation - no relations will be cloned. Same behavior will be for `exclude_association`. **Be aware**! If you wrote: ```ruby class Post < ActiveRecord::Base has_many :comments has_many :tags amoeba do exclude_association :tags include_association :comments, if: :popular? end def popular? likes > 15 end end ``` inclusion strategy will be chosen regardless of the result of `popular?` method call (the same for reverse situation). #### Cloning If you are using a Many-to-Many relationship, you may tell amoeba to actually make duplicates of the original related records rather than merely maintaining association with the original records. Cloning is easy, merely tell amoeba which fields to clone in the same way you tell it which fields to include or exclude. ```ruby class Post < ActiveRecord::Base has_and_belongs_to_many :warnings has_many :post_widgets has_many :widgets, :through => :post_widgets amoeba do enable clone [:widgets, :warnings] end end class Warning < ActiveRecord::Base has_and_belongs_to_many :posts end class PostWidget < ActiveRecord::Base belongs_to :widget belongs_to :post end class Widget < ActiveRecord::Base has_many :post_widgets has_many :posts, :through => :post_widgets end ``` This example will actually duplicate the warnings and widgets in the database. If there were originally 3 warnings in the database then, upon duplicating a post, you will end up with 6 warnings in the database. This is in contrast to the default behavior where your new post would merely be re-associated with any previously existing warnings and those warnings themselves would not be duplicated. #### Limiting Association Types By default, amoeba recognizes and attempts to copy any children of the following association types: - has one - has many - has and belongs to many You may control which association types amoeba applies itself to by using the `recognize` method within the amoeba configuration block. ```ruby class Post < ActiveRecord::Base has_one :config has_many :comments has_and_belongs_to_many :tags amoeba do recognize [:has_one, :has_and_belongs_to_many] end end class Comment < ActiveRecord::Base belongs_to :post end class Tag < ActiveRecord::Base has_and_belongs_to_many :posts end ``` This example will copy the post's configuration data and keep tags associated with the new post, but will not copy the post's comments because amoeba will only recognize and copy children of `has_one` and `has_and_belongs_to_many` associations and in this example, comments are not an `has_and_belongs_to_many` association. ### Field Preprocessors #### Nullify If you wish to prevent a regular (non `has_*` association based) field from retaining it's value when copied, you may "zero out" or "nullify" the field, like this: ```ruby class Topic < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :topic has_many :comments amoeba do enable nullify :date_published nullify :topic_id end end class Comment < ActiveRecord::Base belongs_to :post end ``` This example will copy all of a post's comments. It will also nullify the publishing date and dissociate the post from its original topic. Unlike inclusive and exclusive styles, specifying null fields will not automatically enable amoeba to copy all child records. As with any active record object, the default field value will be used instead of `nil` if a default value exists on the migration. #### Set If you wish to just set a field to an arbitrary value on all duplicated objects you may use the `set` directive. For example, if you wanted to copy an object that has some kind of approval process associated with it, you likely may wish to set the new object's state to be open or "in progress" again. ```ruby class Post < ActiveRecord::Base amoeba do set :state_tracker => "open_for_editing" end end ``` In this example, when a post is duplicated, it's `state_tracker` field will always be given a value of `open_for_editing` to start. #### Prepend You may add a string to the beginning of a copied object's field during the copy phase: ```ruby class Post < ActiveRecord::Base amoeba do enable prepend :title => "Copy of " end end ``` #### Append You may add a string to the end of a copied object's field during the copy phase: ```ruby class Post < ActiveRecord::Base amoeba do enable append :title => "Copy of " end end ``` #### Regex You may run a search and replace query on a copied object's field during the copy phase: ```ruby class Post < ActiveRecord::Base amoeba do enable regex :contents => {:replace => /dog/, :with => 'cat'} end end ``` #### Custom Methods ##### Customize You may run a custom method or methods to do basically anything you like, simply pass a lambda block, or an array of lambda blocks to the `customize` directive. Each block must have the same form, meaning that each block must accept two parameters, the original object and the newly copied object. You may then do whatever you wish, like this: ```ruby class Post < ActiveRecord::Base amoeba do prepend :title => "Hello world! " customize(lambda { |original_post,new_post| if original_post.foo == "bar" new_post.baz = "qux" end }) append :comments => "... know what I'm sayin?" end end ``` or this, using an array: ```ruby class Post < ActiveRecord::Base has_and_belongs_to_many :tags amoeba do include_association :tags customize([ lambda do |orig_obj,copy_of_obj| # good stuff goes here end, lambda do |orig_obj,copy_of_obj| # more good stuff goes here end ]) end end ``` ##### Override Lambda blocks passed to customize run, by default, after all copying and field pre-processing. If you wish to run a method before any customization or field pre-processing, you may use `override` the cousin of `customize`. Usage is the same as above. ```ruby class Post < ActiveRecord::Base amoeba do prepend :title => "Hello world! " override(lambda { |original_post,new_post| if original_post.foo == "bar" new_post.baz = "qux" end }) append :comments => "... know what I'm sayin?" end end ``` #### Chaining You may apply a single preprocessor to multiple fields at once. ```ruby class Post < ActiveRecord::Base amoeba do enable prepend :title => "Copy of ", :contents => "Copied contents: " end end ``` #### Stacking You may apply multiple preprocessing directives to a single model at once. ```ruby class Post < ActiveRecord::Base amoeba do prepend :title => "Copy of ", :contents => "Original contents: " append :contents => " (copied version)" regex :contents => {:replace => /dog/, :with => 'cat'} end end ``` This example should result in something like this: ```ruby post = Post.create( :title => "Hello world", :contents => "I like dogs, dogs are awesome." ) new_post = post.amoeba_dup new_post.title # "Copy of Hello world" new_post.contents # "Original contents: I like cats, cats are awesome. (copied version)" ``` Like `nullify`, the preprocessing directives do not automatically enable the copying of associated child records. If only preprocessing directives are used and you do want to copy child records and no `include_association` or `exclude_association` list is provided, you must still explicitly enable the copying of child records by calling the enable method from within the amoeba block on your model. ### Precedence You may use a combination of configuration methods within each model's amoeba block. Recognized association types take precedence over inclusion or exclusion lists. Inclusive style takes precedence over exclusive style, and these two explicit styles take precedence over the indiscriminate style. In other words, if you list fields to copy, amoeba will only copy the fields you list, or only copy the fields you don't exclude as the case may be. Additionally, if a field type is not recognized it will not be copied, regardless of whether it appears in an inclusion list. If you want amoeba to automatically copy all of your child records, do not list any fields using either `include_association` or `exclude_association`. The following example syntax is perfectly valid, and will result in the usage of inclusive style. The order in which you call the configuration methods within the amoeba block does not matter: ```ruby class Topic < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :topic has_many :comments has_many :tags has_many :authors amoeba do exclude_association :authors include_association :tags nullify :date_published prepend :title => "Copy of " append :contents => " (copied version)" regex :contents => {:replace => /dog/, :with => 'cat'} include_association :authors enable nullify :topic_id end end class Comment < ActiveRecord::Base belongs_to :post end ``` This example will copy all of a post's tags and authors, but not its comments. It will also nullify the publishing date and dissociate the post from its original topic. It will also preprocess the post's fields as in the previous preprocessing example. Note that, because of precedence, inclusive style is used and the list of exclude fields is never consulted. Additionally, the `enable` method is redundant because amoeba is automatically enabled when using `include_association`. The preprocessing directives are run after child records are copied and are run in this order. 1. Null fields 2. Prepends 3. Appends 4. Search and Replace Preprocessing directives do not affect inclusion and exclusion lists. ### Recursing You may cause amoeba to keep copying down the chain as far as you like, simply add amoeba blocks to each model you wish to have copy its children. Amoeba will automatically recurse into any enabled grandchildren and copy them as well. ```ruby class Post < ActiveRecord::Base has_many :comments amoeba do enable end end class Comment < ActiveRecord::Base belongs_to :post has_many :ratings amoeba do enable end end class Rating < ActiveRecord::Base belongs_to :comment end ``` In this example, when a post is copied, amoeba will copy each all of a post's comments and will also copy each comment's ratings. ### Has One Through Using the `has_one :through` association is simple, just be sure to enable amoeba on the each model with a `has_one` association and amoeba will automatically and recursively drill down, like so: ```ruby class Supplier < ActiveRecord::Base has_one :account has_one :history, :through => :account amoeba do enable end end class Account < ActiveRecord::Base belongs_to :supplier has_one :history amoeba do enable end end class History < ActiveRecord::Base belongs_to :account end ``` ### Has Many Through Copying of `has_many :through` associations works automatically. They perform the copy in the same way as the `has_and_belongs_to_many` association, meaning the actual child records are not copied, but rather the associations are simply maintained. You can add some field preprocessors to the middle model if you like but this is not strictly necessary: ```ruby class Assembly < ActiveRecord::Base has_many :manifests has_many :parts, :through => :manifests amoeba do enable end end class Manifest < ActiveRecord::Base belongs_to :assembly belongs_to :part amoeba do prepend :notes => "Copy of " end end class Part < ActiveRecord::Base has_many :manifests has_many :assemblies, :through => :manifests amoeba do enable end end ``` ### On The Fly Configuration You may control how amoeba copies your object, on the fly, by passing a configuration block to the model's amoeba method. The configuration method is static but the configuration is applied on a per instance basis. ```ruby class Post < ActiveRecord::Base has_many :comments amoeba do enable prepend :title => "Copy of " end end class Comment < ActiveRecord::Base belongs_to :post end class PostsController < ActionController def duplicate_a_post old_post = Post.create( :title => "Hello world", :contents => "Lorum ipsum" ) old_post.class.amoeba do prepend :contents => "Here's a copy: " end new_post = old_post.amoeba_dup new_post.title # should be "Copy of Hello world" new_post.contents # should be "Here's a copy: Lorum ipsum" new_post.save end end ``` ### Inheritance If you are using the Single Table Inheritance provided by ActiveRecord, you may cause amoeba to automatically process child classes in the same way as their parents. All you need to do is call the `propagate` method within the amoeba block of the parent class and all child classes should copy in a similar manner. ```ruby create_table :products, :force => true do |t| t.string :type # this is the STI column # these belong to all products t.string :title t.decimal :price # these are for shirts only t.decimal :sleeve_length t.decimal :collar_size # these are for computers only t.integer :ram_size t.integer :hard_drive_size end class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :categories amoeba do enable propagate end end class Shirt < Product end class Computer < Product end class ProductsController def some_method my_shirt = Shirt.find(1) my_shirt.amoeba_dup my_shirt.save # this shirt should now: # - have its own copy of all parent images # - be in the same categories as the parent end end ``` This example should duplicate all the images and sections associated with this Shirt, which is a child of Product #### Parenting Style By default, propagation uses submissive parenting, meaning the config settings on the parent will be applied, but any child settings, if present, will either add to or overwrite the parent settings depending on how you call the DSL methods. You may change this behavior, the so called "parenting style", to give preference to the parent settings or to ignore any and all child settings. ##### Relaxed Parenting The `:relaxed` parenting style will prefer parent settings. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do exclude_association :images propagate :relaxed end end class Shirt < Product include_association :images include_association :sections prepend :title => "Copy of " end ``` In this example, the conflicting `include_association` settings on the child will be ignored and the parent `exclude_association` setting will be used, while the `prepend` setting on the child will be honored because it doesn't conflict with the parent. ##### Strict Parenting The `:strict` style will ignore child settings altogether and inherit any parent settings. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do exclude_association :images propagate :strict end end class Shirt < Product include_association :images include_association :sections prepend :title => "Copy of " end ``` In this example, the only processing that will happen when a Shirt is duplicated is whatever processing is allowed by the parent. So in this case the parent's `exclude_association` directive takes precedence over the child's `include_association` settings, and not only that, but none of the other settings for the child are used either. The `prepend` setting of the child is completely ignored. ##### Parenting and Precedence Because of the two general forms of DSL config parameter usage, you may wish to make yourself mindful of how your coding style will affect the outcome of duplicating an object. Just remember that: * If you pass an array you will wipe all previous settings * If you pass single values, you will add to currently existing settings This means that, for example: * When using the submissive parenting style, you can child take full precedence on a per field basis by passing an array of config values. This will cause the setting from the parent to be overridden instead of added to. * When using the relaxed parenting style, you can still let the parent take precedence on a per field basis by passing an array of config values. This will cause the setting for that child to be overridden instead of added to. ##### A Submissive Override Example This version will use both the parent and child settings, so both the images and sections will be copied. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do include_association :images propagate end end class Shirt < Product include_association :sections end ``` The next version will use only the child settings because passing an array will override any previous settings rather than adding to them and the child config takes precedence in the `submissive` parenting style. So in this case only the sections will be copied. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do include_association :images propagate end end class Shirt < Product include_association [:sections] end ``` ##### A Relaxed Override Example This version will use both the parent and child settings, so both the images and sections will be copied. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do include_association :images propagate :relaxed end end class Shirt < Product include_association :sections end ``` The next version will use only the parent settings because passing an array will override any previous settings rather than adding to them and the parent config takes precedence in the `relaxed` parenting style. So in this case only the images will be copied. ```ruby class Product < ActiveRecord::Base has_many :images has_and_belongs_to_many :sections amoeba do include_association [:images] propagate end end class Shirt < Product include_association :sections end ``` ### Validating Nested Attributes If you end up with some validation issues when trying to validate the presence of a child's `belongs_to` association, just be sure to include the `:inverse_of` declaration on your relationships and all should be well. For example this will throw a validation error saying that your posts are invalid: ```ruby class Author < ActiveRecord::Base has_many :posts amoeba do enable end end class Post < ActiveRecord::Base belongs_to :author validates_presence_of :author amoeba do enable end end author = Author.find(1) author.amoeba_dup author.save # this will fail validation ``` Where this will work fine: ```ruby class Author < ActiveRecord::Base has_many :posts, :inverse_of => :author amoeba do enable end end class Post < ActiveRecord::Base belongs_to :author, :inverse_of => :posts validates_presence_of :author amoeba do enable end end author = Author.find(1) author.amoeba_dup author.save # this will pass validation ``` This issue is not amoeba specific and also occurs when creating new objects using `accepts_nested_attributes_for`, like this: ```ruby class Author < ActiveRecord::Base has_many :posts accepts_nested_attributes_for :posts end class Post < ActiveRecord::Base belongs_to :author validates_presence_of :author end # this will fail validation author = Author.create({:name => "Jim Smith", :posts => [{:title => "Hello World", :contents => "Lorum ipsum dolor}]}) ``` This issue with `accepts_nested_attributes_for` can also be solved by using `:inverse_of`, like this: ```ruby class Author < ActiveRecord::Base has_many :posts, :inverse_of => :author accepts_nested_attributes_for :posts end class Post < ActiveRecord::Base belongs_to :author, :inverse_of => :posts validates_presence_of :author end # this will pass validation author = Author.create({:name => "Jim Smith", :posts => [{:title => "Hello World", :contents => "Lorum ipsum dolor}]}) ``` The crux of the issue is that upon duplication, the new `Author` instance does not yet have an ID because it has not yet been persisted, so the `:posts` do not yet have an `:author_id` either, and thus no `:author` and thus they will fail validation. This issue may likely affect amoeba usage so if you get some validation failures, be sure to add `:inverse_of` to your models. ## Cloning using custom method If you need to clone model with custom method you can use `through`: ```ruby class ChildPrototype < ActiveRecord::Base amoeba do through :become_child end def become_child self.dup.becomes(Child) end end class Child < ChildPrototype end ``` After cloning we will get instance of `Child` instead of `ChildPrototype` ## Remapping associations If you will need to do complex cloning with remapping associations name you can user `remapper`: ```ruby class ObjectPrototype < ActiveRecord::Base has_many :child_prototypes amoeba do method :become_real remapper :remap_associations end def become_real self.dup().becomes( RealObject ) end def remap_associations( name ) :childs if name == :child_prototypes end end class RealObject < ObjectPrototype has_many :childs end class ChildPrototype < ActiveRecord::Base amoeba do method :become_child end def become_child self.dup().becomes( Child ) end end class Child < ChildPrototype end ``` In result we will get next: ```ruby prototype = ObjectPrototype.new prototype.child_prototypes << ChildPrototype.new object = prototype.amoeba_dup object.class # => RealObject object.childs.first.class #=> Child ``` ## Configuration Reference Here is a static reference to the available configuration methods, usable within the amoeba block on your rails models. ### through Set method what we will use for cloning model instead of `dup`. for example: ```ruby amoeba do through :supper_pupper_dup end def supper_pupper_dup puts "multiplied by budding" self.dup end ``` ### Controlling Associations #### enable Enables amoeba in the default style of copying all known associated child records. Using the enable method is only required if you wish to enable amoeba but you are not using either the `include_association` or `exclude_association` directives. If you use either inclusive or exclusive style, amoeba is automatically enabled for you, so calling `enable` would be redundant, though it won't hurt. #### include_association Adds a field to the list of fields which should be copied. All associations not in this list will not be copied. This method may be called multiple times, once per desired field, or you may pass an array of field names. Passing a single symbol will add to the list of included fields. Passing an array will empty the list and replace it with the array you pass. #### exclude_association Adds a field to the list of fields which should not be copied. Only the associations that are not in this list will be copied. This method may be called multiple times, once per desired field, or you may pass an array of field names. Passing a single symbol will add to the list of excluded fields. Passing an array will empty the list and replace it with the array you pass. #### clone Adds a field to the list of associations which should have their associated children actually cloned. This means for example, that instead of just maintaining original associations with previously existing tags, a copy will be made of each tag, and the new record will be associated with these new tag copies rather than the old tag copies. This method may be called multiple times, once per desired field, or you may pass an array of field names. Passing a single symbol will add to the list of excluded fields. Passing an array will empty the list and replace it with the array you pass. #### propagate This causes any inherited child models to take the same config settings when copied. This method may take up to one argument to control the so called "parenting style". The argument should be one of `strict`, `relaxed` or `submissive`. The default "parenting style" is `submissive` for example ```ruby amoeba do propagate :strict end ``` will choose the strict parenting style of inherited settings. #### raised This causes any child to behave with a (potentially) different "parenting style" than its actual parent. This method takes up to a single parameter for which there are three options, `strict`, `relaxed` and `submissive`. The default "parenting style" is `submissive` for example: ```ruby amoeba do raised :relaxed end ``` will choose the relaxed parenting style of inherited settings for this child. A parenting style set via the `raised` method takes precedence over the parenting style set using the `propagate` method. #### remapper Set the method what will be used for remapping of association name. Method will have one argument - association name as Symbol. If method will return nil then association will not be remapped. for example: ```ruby amoeba do remapper :childs_to_parents end def childs_to_parents(association_name) :parents if association_name == :childs end ``` ### Pre-Processing Fields #### nullify Adds a field to the list of non-association based fields which should be set to nil during copy. All fields in this list will be set to `nil` - note that any nullified field will be given its default value if a default value exists on this model's migration. This method may be called multiple times, once per desired field, or you may pass an array of field names. Passing a single symbol will add to the list of null fields. Passing an array will empty the list and replace it with the array you pass. #### prepend Prefix a field with some text. This only works for string fields. Accepts a hash of fields to prepend. The keys are the field names and the values are the prefix strings. An example scenario would be to add a string such as "Copy of " to your title field. Don't forget to include extra space to the right if you want it. Passing a hash will add each key value pair to the list of prepend directives. If you wish to empty the list of directives, you may pass the hash inside of an array like this `[{:title => "Copy of "}]`. #### append Append some text to a field. This only works for string fields. Accepts a hash of fields to prepend. The keys are the field names and the values are the prefix strings. An example would be to add " (copied version)" to your description field. Don't forget to add a leading space if you want it. Passing a hash will add each key value pair to the list of append directives. If you wish to empty the list of directives, you may pass the hash inside of an array like this `[{:contents => " (copied version)"}]`. #### set Set a field to a given value. This should work for almost any type of field. Accepts a hash of fields and the values you want them set to.. The keys are the field names and the values are the prefix strings. An example would be to add " (copied version)" to your description field. Don't forget to add a leading space if you want it. Passing a hash will add each key value pair to the list of append directives. If you wish to empty the list of directives, you may pass the hash inside of an array like this `[{:approval_state => "open_for_editing"}]`. #### regex Globally search and replace the field for a given pattern. Accepts a hash of fields to run search and replace upon. The keys are the field names and the values are each a hash with information about what to find and what to replace it with. in the form of . An example would be to replace all occurrences of the word "dog" with the word "cat", the parameter hash would look like this `:contents => {:replace => /dog/, :with => "cat"}`. Passing a hash will add each key value pair to the list of regex directives. If you wish to empty the list of directives, you may pass the hash inside of an array like this `[{:contents => {:replace => /dog/, :with => "cat"}]`. #### override Runs a custom method so you can do basically whatever you want. All you need to do is pass a lambda block or an array of lambda blocks that take two parameters, the original object and the new object copy. These blocks will run before any other duplication or field processing. This method may be called multiple times, once per desired customizer block, or you may pass an array of lambdas. Passing a single lambda will add to the list of processing directives. Passing an array will empty the list and replace it with the array you pass. #### customize Runs a custom method so you can do basically whatever you want. All you need to do is pass a lambda block or an array of lambda blocks that take two parameters, the original object and the new object copy. These blocks will run after all copying and field processing. This method may be called multiple times, once per desired customizer block, or you may pass an array of lambdas. Passing a single lambda will add to the list of processing directives. Passing an array will empty the list and replace it with the array you pass. ## Known Limitations and Issues The regular expression preprocessor uses case-sensitive `String#gsub`. Given the performance decreases inherrent in using regular expressions already, the fact that character classes can essentially account for case-insensitive searches, the desire to keep the DSL simple and the general use cases for this gem, I don't see a good reason to add yet more decision based conditional syntax to accommodate using case-insensitive searches or singular replacements with `String#sub`. If you find yourself wanting either of these features, by all means fork the code base and if you like your changes, submit a pull request. The behavior when copying nested hierarchical models is undefined. Copying a category model which has a `parent_id` field pointing to the parent category, for example, is currently undefined. The behavior when copying polymorphic `has_many` associations is also undefined. Support for these types of associations is planned for a future release. ## For Developers You may run the rspec tests like this: ```sh bundle exec rspec spec ``` ### TODO * add ability to cancel further processing from within an override block * write some spec for the override method ## License [The BSD License](http://www.opensource.org/licenses/bsd-license.php) Copyright (c) 2012, Vaughn Draughon All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 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