# Jb
A simpler and faster Jbuilder alternative.
## Installation
Add this line to your application's Gemfile:
```ruby
gem 'jb'
```
And bundle.
## Usage
Put a template file named `*.jb` in your Rails app's `app/views/*` directory, and render it.
## Features
* No ugly builder syntax
* No `method_missing` calls
* `render_partial` with :collection option actually renders the collection (unlike Jbuilder)
## Syntax
A `.jb` template should contain Ruby code that returns any Ruby Object that responds_to `to_json` (generally Hash or Array).
Then the return value will be `to_json`ed to a JSON String.
## Examples
``` ruby
# app/views/messages/show.json.jb
json = {
content: format_content(@message.content),
created_at: @message.created_at,
updated_at: @message.updated_at,
author: {
name: @message.creator.name.familiar,
email_address: @message.creator.email_address_with_name,
url: url_for(@message.creator, format: :json)
}
}
if current_user.admin?
json[:visitors] = calculate_visitors(@message)
end
json[:comments] = {
content: @message.comments.content,
created_at: @message.comments.created_at
}
json[:attachments] = @message.attachments.map do |attachment|
filename: attachment.filename,
url: url_for(attachment)
end
json
```
This will build the following structure:
``` javascript
{
"content": "10x JSON",
"created_at": "2016-06-29T20:45:28-05:00",
"updated_at": "2016-06-29T20:45:28-05:00",
"author": {
"name": "Yukihiro Matz",
"email_address": "matz@example.com",
"url": "http://example.com/users/1-matz.json"
},
"visitors": 1326,
"comments": [
{ "content": "Hello, world!", "created_at": "2016-06-29T20:45:28-05:00" },
{ "content": "<script>alert('Hello, world!');</script>", "created_at": "2016-06-29T20:47:28-05:00" }
],
"attachments": [
{ "filename": "sushi.png", "url": "http://example.com/downloads/sushi.png" },
{ "filename": "sake.jpg", "url": "http://example.com/downloads/sake.jpg" }
]
}
```
To define attribute and structure names dynamically, just use Ruby Hash.
Note that modern Ruby Hash syntax pretty much looks alike JSON syntax.
It's super-straight forward. Who needs a DSL to do this?
``` ruby
{author: {name: 'Matz'}}
# => {"author": {"name": "Matz"}}
```
Top level arrays can be handled directly. Useful for index and other collection actions.
And you know, Ruby is such a powerful language for manipulating collections:
``` ruby
# @comments = @post.comments
@comments.reject {|c| c.marked_as_spam_by?(current_user) }.map do |comment|
body: comment.body,
author: {
first_name: comment.author.first_name,
last_name: comment.author.last_name
}
end
# => [{"body": "🍣 is omakase...", "author": {"first_name": "Yukihiro", "last_name": "Matz"}}]
```
Jb has no special DSL method for extracting attributes from array directly, but you can do that with Ruby.
``` ruby
# @people = People.all
@people.map {|p| {id: p.id, name: p.name}}
# => [{"id": 1, "name": "Matz"}, {"id": 2, "name": "Nobu"}]
```
You can use Jb directly as an Action View template language.
When required in Rails, you can create views ala show.json.jb.
You'll notice in the following example that the `.jb` template
doesn't have to be one big Ruby Hash literal as a whole
but it can be any Ruby code that finally returns a Hash instance.
``` ruby
# Any helpers available to views are available in the template
json = {
content: format_content(@message.content),
created_at: @message.created_at,
updated_at: @message.updated_at,
author: {
name: @message.creator.name.familiar,
email_address: @message.creator.email_address_with_name,
url: url_for(@message.creator, format: :json)
}
}
if current_user.admin?
json[:visitors] = calculate_visitors(@message)
end
json
```
You can use partials as well. The following will render the file
`views/comments/_comments.json.jb`, and set a local variable
`comments` with all this message's comments, which you can use inside
the partial.
```ruby
render 'comments/comments', comments: @message.comments
```
It's also possible to render collections of partials:
```ruby
render partial: 'posts/post', collection: @posts, as: :post
# or
render @post.comments
```
You can pass any objects into partial templates with or without `:locals` option.
```ruby
render 'sub_template', locals: {user: user}
# or
render 'sub_template', user: user
```
You can of course include Ruby `nil` as a Hash value if you want. That would become `null` in the JSON.
To prevent Jb from including null values in the output, Active Support provides `Hash#compact!` method for you:
```ruby
{foo: nil, bar: 'bar'}.compact
# => {"bar": "bar"}
```
If you want to cache a template fragment, just directly call `Rails.cache.fetch`:
```ruby
Rails.cache.fetch ['v1', @person], expires_in: 10.minutes do
{name: @person.name, age: @person.age}
end
```
## The Generator
Jb extends the default Rails scaffold generator and adds some .jb templates.
If you don't need them, please configure like so.
```ruby
Rails.application.config.generators.jb false
```
## Why is Jb fast?
Jbuilder's `partial` + `:collection` [internally calls `array!` method](https://github.com/rails/jbuilder/blob/83a682aeebde96c6ef02ce742c0b97dc393f5e22/lib/jbuilder/jbuilder_template.rb#L85-L95)
inside which [`_render_partial` is called per each element of the given collection](https://github.com/rails/jbuilder/blob/83a682aeebde96c6ef02ce742c0b97dc393f5e22/lib/jbuilder/jbuilder_template.rb#L93),
and then it [falls back to the `view_context`'s `render` method](https://github.com/rails/jbuilder/blob/83a682aeebde96c6ef02ce742c0b97dc393f5e22/lib/jbuilder/jbuilder_template.rb#L100-L103).
So, for example if the collection has 100 elements, Jbuilder's `render partial:` performs `render` method 100 times, and so it calls `find_template` method (which is known as one of the heaviest parts of Action View) 100 times.
OTOH, Jb simply calls [ActionView::PartialRenderer's `render`](https://github.com/rails/rails/blob/49a881e0db1ef64fcbae2b7ddccfd5ccea26ae01/actionview/lib/action_view/renderer/partial_renderer.rb#L423-L443) which is cleverly implmented to `find_template` only once beforehand, then pass each element to that template.
## Benchmarks
Here're the results of a benchmark (which you can find [here](https://github.com/amatsuda/jb/blob/master/test/dummy_app/app/controllers/benchmarks_controller.rb) in this repo) rendering a collection to JSON.
### RAILS_ENV=development
```
% ./bin/benchmark.sh
* Rendering 10 partials via render_partial
Warming up --------------------------------------
jb 15.000 i/100ms
jbuilder 8.000 i/100ms
Calculating -------------------------------------
jb 156.375 (± 7.0%) i/s - 780.000 in 5.016581s
jbuilder 87.890 (± 6.8%) i/s - 440.000 in 5.037225s
Comparison:
jb: 156.4 i/s
jbuilder: 87.9 i/s - 1.78x slower
* Rendering 100 partials via render_partial
Warming up --------------------------------------
jb 13.000 i/100ms
jbuilder 1.000 i/100ms
Calculating -------------------------------------
jb 121.187 (±14.0%) i/s - 598.000 in 5.049667s
jbuilder 11.478 (±26.1%) i/s - 54.000 in 5.061996s
Comparison:
jb: 121.2 i/s
jbuilder: 11.5 i/s - 10.56x slower
* Rendering 1000 partials via render_partial
Warming up --------------------------------------
jb 4.000 i/100ms
jbuilder 1.000 i/100ms
Calculating -------------------------------------
jb 51.472 (± 7.8%) i/s - 256.000 in 5.006584s
jbuilder 1.510 (± 0.0%) i/s - 8.000 in 5.383548s
Comparison:
jb: 51.5 i/s
jbuilder: 1.5 i/s - 34.08x slower
```
### RAILS_ENV=production
```
% RAILS_ENV=production ./bin/benchmark.sh
* Rendering 10 partials via render_partial
Warming up --------------------------------------
jb 123.000 i/100ms
jbuilder 41.000 i/100ms
Calculating -------------------------------------
jb 1.406k (± 4.2%) i/s - 7.134k in 5.084030s
jbuilder 418.360 (± 9.8%) i/s - 2.091k in 5.043381s
Comparison:
jb: 1405.8 i/s
jbuilder: 418.4 i/s - 3.36x slower
* Rendering 100 partials via render_partial
Warming up --------------------------------------
jb 37.000 i/100ms
jbuilder 5.000 i/100ms
Calculating -------------------------------------
jb 383.082 (± 8.4%) i/s - 1.924k in 5.061973s
jbuilder 49.914 (± 8.0%) i/s - 250.000 in 5.040364s
Comparison:
jb: 383.1 i/s
jbuilder: 49.9 i/s - 7.67x slower
* Rendering 1000 partials via render_partial
Warming up --------------------------------------
jb 4.000 i/100ms
jbuilder 1.000 i/100ms
Calculating -------------------------------------
jb 43.017 (± 9.3%) i/s - 216.000 in 5.080482s
jbuilder 4.604 (±21.7%) i/s - 23.000 in 5.082100s
Comparison:
jb: 43.0 i/s
jbuilder: 4.6 i/s - 9.34x slower
```
### Summary
According to the benchmark results, you can expect 2-30x performance improvement in development env, and 3-10x performance improvement in production env.
## Contributing
Pull requests are welcome on GitHub at https://github.com/amatsuda/jb.
## License
The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).