mirror of
https://github.com/rails/rails.git
synced 2022-11-09 12:12:34 -05:00
484 lines
13 KiB
Markdown
484 lines
13 KiB
Markdown
**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.**
|
|
|
|
The Basics of Creating Rails Plugins
|
|
====================================
|
|
|
|
A Rails plugin is either an extension or a modification of the core framework. Plugins provide:
|
|
|
|
* A way for developers to share bleeding-edge ideas without hurting the stable code base.
|
|
* A segmented architecture so that units of code can be fixed or updated on their own release schedule.
|
|
* An outlet for the core developers so that they don't have to include every cool new feature under the sun.
|
|
|
|
After reading this guide, you will know:
|
|
|
|
* How to create a plugin from scratch.
|
|
* How to write and run tests for the plugin.
|
|
|
|
This guide describes how to build a test-driven plugin that will:
|
|
|
|
* Extend core Ruby classes like Hash and String.
|
|
* Add methods to `ApplicationRecord` in the tradition of the `acts_as` plugins.
|
|
* Give you information about where to put generators in your plugin.
|
|
|
|
For the purpose of this guide pretend for a moment that you are an avid bird watcher.
|
|
Your favorite bird is the Yaffle, and you want to create a plugin that allows other developers to share in the Yaffle
|
|
goodness.
|
|
|
|
--------------------------------------------------------------------------------
|
|
|
|
Setup
|
|
-----
|
|
|
|
Currently, Rails plugins are built as gems, _gemified plugins_. They can be shared across
|
|
different Rails applications using RubyGems and Bundler if desired.
|
|
|
|
### Generate a gemified plugin.
|
|
|
|
|
|
Rails ships with a `rails plugin new` command which creates a
|
|
skeleton for developing any kind of Rails extension with the ability
|
|
to run integration tests using a dummy Rails application. Create your
|
|
plugin with the command:
|
|
|
|
```bash
|
|
$ rails plugin new yaffle
|
|
```
|
|
|
|
See usage and options by asking for help:
|
|
|
|
```bash
|
|
$ rails plugin new --help
|
|
```
|
|
|
|
Testing Your Newly Generated Plugin
|
|
-----------------------------------
|
|
|
|
You can navigate to the directory that contains the plugin, run the `bundle install` command
|
|
and run the one generated test using the `bin/test` command.
|
|
|
|
You should see:
|
|
|
|
```bash
|
|
1 runs, 1 assertions, 0 failures, 0 errors, 0 skips
|
|
```
|
|
|
|
This will tell you that everything got generated properly and you are ready to start adding functionality.
|
|
|
|
Extending Core Classes
|
|
----------------------
|
|
|
|
This section will explain how to add a method to String that will be available anywhere in your Rails application.
|
|
|
|
In this example you will add a method to String named `to_squawk`. To begin, create a new test file with a few assertions:
|
|
|
|
```ruby
|
|
# yaffle/test/core_ext_test.rb
|
|
|
|
require "test_helper"
|
|
|
|
class CoreExtTest < ActiveSupport::TestCase
|
|
def test_to_squawk_prepends_the_word_squawk
|
|
assert_equal "squawk! Hello World", "Hello World".to_squawk
|
|
end
|
|
end
|
|
```
|
|
|
|
Run `bin/test` to run the test. This test should fail because we haven't implemented the `to_squawk` method:
|
|
|
|
```bash
|
|
E
|
|
|
|
Error:
|
|
CoreExtTest#test_to_squawk_prepends_the_word_squawk:
|
|
NoMethodError: undefined method `to_squawk' for "Hello World":String
|
|
|
|
|
|
bin/test /path/to/yaffle/test/core_ext_test.rb:4
|
|
|
|
.
|
|
|
|
Finished in 0.003358s, 595.6483 runs/s, 297.8242 assertions/s.
|
|
|
|
2 runs, 1 assertions, 0 failures, 1 errors, 0 skips
|
|
```
|
|
|
|
Great - now you are ready to start development.
|
|
|
|
In `lib/yaffle.rb`, add `require "yaffle/core_ext"`:
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle.rb
|
|
|
|
require "yaffle/railtie"
|
|
require "yaffle/core_ext"
|
|
|
|
module Yaffle
|
|
# Your code goes here...
|
|
end
|
|
```
|
|
|
|
Finally, create the `core_ext.rb` file and add the `to_squawk` method:
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle/core_ext.rb
|
|
|
|
class String
|
|
def to_squawk
|
|
"squawk! #{self}".strip
|
|
end
|
|
end
|
|
```
|
|
|
|
To test that your method does what it says it does, run the unit tests with `bin/test` from your plugin directory.
|
|
|
|
```bash
|
|
2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
|
|
```
|
|
|
|
To see this in action, change to the `test/dummy` directory, fire up a console, and start squawking:
|
|
|
|
```bash
|
|
$ rails console
|
|
>> "Hello World".to_squawk
|
|
=> "squawk! Hello World"
|
|
```
|
|
|
|
Add an "acts_as" Method to Active Record
|
|
----------------------------------------
|
|
|
|
A common pattern in plugins is to add a method called `acts_as_something` to models. In this case, you
|
|
want to write a method called `acts_as_yaffle` that adds a `squawk` method to your Active Record models.
|
|
|
|
To begin, set up your files so that you have:
|
|
|
|
```ruby
|
|
# yaffle/test/acts_as_yaffle_test.rb
|
|
|
|
require "test_helper"
|
|
|
|
class ActsAsYaffleTest < ActiveSupport::TestCase
|
|
end
|
|
```
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle.rb
|
|
|
|
require "yaffle/railtie"
|
|
require "yaffle/core_ext"
|
|
require "yaffle/acts_as_yaffle"
|
|
|
|
module Yaffle
|
|
# Your code goes here...
|
|
end
|
|
```
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle/acts_as_yaffle.rb
|
|
|
|
module Yaffle
|
|
module ActsAsYaffle
|
|
end
|
|
end
|
|
```
|
|
|
|
### Add a Class Method
|
|
|
|
This plugin will expect that you've added a method to your model named `last_squawk`. However, the
|
|
plugin users might have already defined a method on their model named `last_squawk` that they use
|
|
for something else. This plugin will allow the name to be changed by adding a class method called `yaffle_text_field`.
|
|
|
|
To start out, write a failing test that shows the behavior you'd like:
|
|
|
|
```ruby
|
|
# yaffle/test/acts_as_yaffle_test.rb
|
|
|
|
require "test_helper"
|
|
|
|
class ActsAsYaffleTest < ActiveSupport::TestCase
|
|
def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
|
|
assert_equal "last_squawk", Hickwall.yaffle_text_field
|
|
end
|
|
|
|
def test_a_wickwalls_yaffle_text_field_should_be_last_tweet
|
|
assert_equal "last_tweet", Wickwall.yaffle_text_field
|
|
end
|
|
end
|
|
```
|
|
|
|
When you run `bin/test`, you should see the following:
|
|
|
|
```
|
|
# Running:
|
|
|
|
..E
|
|
|
|
Error:
|
|
ActsAsYaffleTest#test_a_wickwalls_yaffle_text_field_should_be_last_tweet:
|
|
NameError: uninitialized constant ActsAsYaffleTest::Wickwall
|
|
|
|
|
|
bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:8
|
|
|
|
E
|
|
|
|
Error:
|
|
ActsAsYaffleTest#test_a_hickwalls_yaffle_text_field_should_be_last_squawk:
|
|
NameError: uninitialized constant ActsAsYaffleTest::Hickwall
|
|
|
|
|
|
bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:4
|
|
|
|
|
|
|
|
Finished in 0.004812s, 831.2949 runs/s, 415.6475 assertions/s.
|
|
|
|
4 runs, 2 assertions, 0 failures, 2 errors, 0 skips
|
|
```
|
|
|
|
This tells us that we don't have the necessary models (Hickwall and Wickwall) that we are trying to test.
|
|
We can easily generate these models in our "dummy" Rails application by running the following commands from the
|
|
`test/dummy` directory:
|
|
|
|
```bash
|
|
$ cd test/dummy
|
|
$ rails generate model Hickwall last_squawk:string
|
|
$ rails generate model Wickwall last_squawk:string last_tweet:string
|
|
```
|
|
|
|
Now you can create the necessary database tables in your testing database by navigating to your dummy app
|
|
and migrating the database. First, run:
|
|
|
|
```bash
|
|
$ cd test/dummy
|
|
$ rails db:migrate
|
|
```
|
|
|
|
While you are here, change the Hickwall and Wickwall models so that they know that they are supposed to act
|
|
like yaffles.
|
|
|
|
```ruby
|
|
# test/dummy/app/models/hickwall.rb
|
|
|
|
class Hickwall < ApplicationRecord
|
|
acts_as_yaffle
|
|
end
|
|
|
|
# test/dummy/app/models/wickwall.rb
|
|
|
|
class Wickwall < ApplicationRecord
|
|
acts_as_yaffle yaffle_text_field: :last_tweet
|
|
end
|
|
```
|
|
|
|
We will also add code to define the `acts_as_yaffle` method.
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle/acts_as_yaffle.rb
|
|
|
|
module Yaffle
|
|
module ActsAsYaffle
|
|
extend ActiveSupport::Concern
|
|
|
|
class_methods do
|
|
def acts_as_yaffle(options = {})
|
|
end
|
|
end
|
|
end
|
|
end
|
|
|
|
# test/dummy/app/models/application_record.rb
|
|
|
|
class ApplicationRecord < ActiveRecord::Base
|
|
include Yaffle::ActsAsYaffle
|
|
|
|
self.abstract_class = true
|
|
end
|
|
```
|
|
|
|
You can then return to the root directory (`cd ../..`) of your plugin and rerun the tests using `bin/test`.
|
|
|
|
```
|
|
# Running:
|
|
|
|
.E
|
|
|
|
Error:
|
|
ActsAsYaffleTest#test_a_hickwalls_yaffle_text_field_should_be_last_squawk:
|
|
NoMethodError: undefined method `yaffle_text_field' for #<Class:0x0055974ebbe9d8>
|
|
|
|
|
|
bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:4
|
|
|
|
E
|
|
|
|
Error:
|
|
ActsAsYaffleTest#test_a_wickwalls_yaffle_text_field_should_be_last_tweet:
|
|
NoMethodError: undefined method `yaffle_text_field' for #<Class:0x0055974eb8cfc8>
|
|
|
|
|
|
bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:8
|
|
|
|
.
|
|
|
|
Finished in 0.008263s, 484.0999 runs/s, 242.0500 assertions/s.
|
|
|
|
4 runs, 2 assertions, 0 failures, 2 errors, 0 skips
|
|
```
|
|
|
|
Getting closer... Now we will implement the code of the `acts_as_yaffle` method to make the tests pass.
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle/acts_as_yaffle.rb
|
|
|
|
module Yaffle
|
|
module ActsAsYaffle
|
|
extend ActiveSupport::Concern
|
|
|
|
class_methods do
|
|
def acts_as_yaffle(options = {})
|
|
cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s
|
|
end
|
|
end
|
|
end
|
|
end
|
|
|
|
# test/dummy/app/models/application_record.rb
|
|
|
|
class ApplicationRecord < ActiveRecord::Base
|
|
include Yaffle::ActsAsYaffle
|
|
|
|
self.abstract_class = true
|
|
end
|
|
```
|
|
|
|
When you run `bin/test`, you should see the tests all pass:
|
|
|
|
```bash
|
|
4 runs, 4 assertions, 0 failures, 0 errors, 0 skips
|
|
```
|
|
|
|
### Add an Instance Method
|
|
|
|
This plugin will add a method named 'squawk' to any Active Record object that calls `acts_as_yaffle`. The 'squawk'
|
|
method will simply set the value of one of the fields in the database.
|
|
|
|
To start out, write a failing test that shows the behavior you'd like:
|
|
|
|
```ruby
|
|
# yaffle/test/acts_as_yaffle_test.rb
|
|
require "test_helper"
|
|
|
|
class ActsAsYaffleTest < ActiveSupport::TestCase
|
|
def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
|
|
assert_equal "last_squawk", Hickwall.yaffle_text_field
|
|
end
|
|
|
|
def test_a_wickwalls_yaffle_text_field_should_be_last_tweet
|
|
assert_equal "last_tweet", Wickwall.yaffle_text_field
|
|
end
|
|
|
|
def test_hickwalls_squawk_should_populate_last_squawk
|
|
hickwall = Hickwall.new
|
|
hickwall.squawk("Hello World")
|
|
assert_equal "squawk! Hello World", hickwall.last_squawk
|
|
end
|
|
|
|
def test_wickwalls_squawk_should_populate_last_tweet
|
|
wickwall = Wickwall.new
|
|
wickwall.squawk("Hello World")
|
|
assert_equal "squawk! Hello World", wickwall.last_tweet
|
|
end
|
|
end
|
|
```
|
|
|
|
Run the test to make sure the last two tests fail with an error that contains "NoMethodError: undefined method `squawk'",
|
|
then update `acts_as_yaffle.rb` to look like this:
|
|
|
|
```ruby
|
|
# yaffle/lib/yaffle/acts_as_yaffle.rb
|
|
|
|
module Yaffle
|
|
module ActsAsYaffle
|
|
extend ActiveSupport::Concern
|
|
|
|
included do
|
|
def squawk(string)
|
|
write_attribute(self.class.yaffle_text_field, string.to_squawk)
|
|
end
|
|
end
|
|
|
|
class_methods do
|
|
def acts_as_yaffle(options = {})
|
|
cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s
|
|
end
|
|
end
|
|
end
|
|
end
|
|
|
|
# test/dummy/app/models/application_record.rb
|
|
|
|
class ApplicationRecord < ActiveRecord::Base
|
|
include Yaffle::ActsAsYaffle
|
|
|
|
self.abstract_class = true
|
|
end
|
|
```
|
|
|
|
Run `bin/test` one final time and you should see:
|
|
|
|
```
|
|
6 runs, 6 assertions, 0 failures, 0 errors, 0 skips
|
|
```
|
|
|
|
NOTE: The use of `write_attribute` to write to the field in model is just one example of how a plugin can interact with the model, and will not always be the right method to use. For example, you could also use:
|
|
|
|
```ruby
|
|
send("#{self.class.yaffle_text_field}=", string.to_squawk)
|
|
```
|
|
|
|
Generators
|
|
----------
|
|
|
|
Generators can be included in your gem simply by creating them in a `lib/generators` directory of your plugin. More information about
|
|
the creation of generators can be found in the [Generators Guide](generators.html).
|
|
|
|
Publishing Your Gem
|
|
-------------------
|
|
|
|
Gem plugins currently in development can easily be shared from any Git repository. To share the Yaffle gem with others, simply
|
|
commit the code to a Git repository (like GitHub) and add a line to the `Gemfile` of the application in question:
|
|
|
|
```ruby
|
|
gem "yaffle", git: "https://github.com/rails/yaffle.git"
|
|
```
|
|
|
|
After running `bundle install`, your gem functionality will be available to the application.
|
|
|
|
When the gem is ready to be shared as a formal release, it can be published to [RubyGems](https://rubygems.org).
|
|
For more information about publishing gems to RubyGems, see: [Publishing your gem](https://guides.rubygems.org/publishing).
|
|
|
|
RDoc Documentation
|
|
------------------
|
|
|
|
Once your plugin is stable and you are ready to deploy, do everyone else a favor and document it! Luckily, writing documentation for your plugin is easy.
|
|
|
|
The first step is to update the README file with detailed information about how to use your plugin. A few key things to include are:
|
|
|
|
* Your name
|
|
* How to install
|
|
* How to add the functionality to the app (several examples of common use cases)
|
|
* Warnings, gotchas or tips that might help users and save them time
|
|
|
|
Once your README is solid, go through and add rdoc comments to all of the methods that developers will use. It's also customary to add `#:nodoc:` comments to those parts of the code that are not included in the public API.
|
|
|
|
Once your comments are good to go, navigate to your plugin directory and run:
|
|
|
|
```bash
|
|
$ bundle exec rake rdoc
|
|
```
|
|
|
|
### References
|
|
|
|
* [Developing a RubyGem using Bundler](https://github.com/radar/guides/blob/master/gem-development.md)
|
|
* [Using .gemspecs as Intended](http://yehudakatz.com/2010/04/02/using-gemspecs-as-intended/)
|
|
* [Gemspec Reference](https://guides.rubygems.org/specification-reference/)
|