== Add an `acts_as_yaffle` method to ActiveRecord ==
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 models.
To keep things clean, create a new test file called 'acts_as_yaffle_test.rb' in your plugin's test directory and require your test helper.
[source, ruby]
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# File: vendor/plugins/yaffle/test/acts_as_yaffle_test.rb
require File.dirname(__FILE__) + '/test_helper.rb'
class Hickwall < ActiveRecord::Base
acts_as_yaffle
end
class ActsAsYaffleTest < Test::Unit::TestCase
end
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[source, ruby]
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# File: vendor/plugins/lib/acts_as_yaffle.rb
module Yaffle
end
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One of the most common plugin patterns for `acts_as_yaffle` plugins is to structure your file like so:
[source, ruby]
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module Yaffle
def self.included(base)
base.send :extend, ClassMethods
end
module ClassMethods
# any method placed here will apply to classes, like Hickwall
def acts_as_something
send :include, InstanceMethods
end
end
module InstanceMethods
# any method placed here will apply to instaces, like @hickwall
end
end
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With structure you can easily separate the methods that will be used for the class (like `Hickwall.some_method`) and the instance (like `@hickwell.some_method`).
Let's add class method named `acts_as_yaffle` - testing it out first. You already defined the ActiveRecord models in your test helper, so if you run tests now they will fail.
Back in your `acts_as_yaffle` file, update ClassMethods like so:
[source, ruby]
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module ClassMethods
def acts_as_yaffle(options = {})
send :include, InstanceMethods
end
end
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Now that test should pass. Since your plugin is going to work with field names, you need to allow people to define the field names, in case there is a naming conflict. You can write a few simple tests for this:
[source, ruby]
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# File: vendor/plugins/yaffle/test/acts_as_yaffle_test.rb
require File.dirname(__FILE__) + '/test_helper.rb'
class ActsAsYaffleTest < Test::Unit::TestCase
def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
assert_equal "last_squawk", Hickwall.yaffle_text_field
end
def test_a_hickwalls_yaffle_date_field_should_be_last_squawked_at
assert_equal "last_squawked_at", Hickwall.yaffle_date_field
end
def test_a_wickwalls_yaffle_text_field_should_be_last_tweet
assert_equal "last_tweet", Wickwall.yaffle_text_field
end
def test_a_wickwalls_yaffle_date_field_should_be_last_tweeted_at
assert_equal "last_tweeted_at", Wickwall.yaffle_date_field
end
end
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To make these tests pass, you could modify your `acts_as_yaffle` file like so:
[source, ruby]
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# File: vendor/plugins/yaffle/lib/acts_as_yaffle.rb
module Yaffle
def self.included(base)
base.send :extend, ClassMethods
end
module ClassMethods
def acts_as_yaffle(options = {})
cattr_accessor :yaffle_text_field, :yaffle_date_field
self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
self.yaffle_date_field = (options[:yaffle_date_field] || :last_squawked_at).to_s
send :include, InstanceMethods
end
end
module InstanceMethods
end
end
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Now you can add tests for the instance methods, and the instance method itself:
[source, ruby]
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# File: vendor/plugins/yaffle/test/acts_as_yaffle_test.rb
require File.dirname(__FILE__) + '/test_helper.rb'
class ActsAsYaffleTest < Test::Unit::TestCase
def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
assert_equal "last_squawk", Hickwall.yaffle_text_field
end
def test_a_hickwalls_yaffle_date_field_should_be_last_squawked_at
assert_equal "last_squawked_at", Hickwall.yaffle_date_field
end
def test_a_wickwalls_yaffle_text_field_should_be_last_squawk
assert_equal "last_tweet", Wickwall.yaffle_text_field
end
def test_a_wickwalls_yaffle_date_field_should_be_last_squawked_at
assert_equal "last_tweeted_at", Wickwall.yaffle_date_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_hickwalls_squawk_should_populate_last_squawked_at
hickwall = Hickwall.new
hickwall.squawk("Hello World")
assert_equal Date.today, hickwall.last_squawked_at
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
def test_wickwalls_squawk_should_populate_last_tweeted_at
wickwall = Wickwall.new
wickwall.squawk("Hello World")
assert_equal Date.today, wickwall.last_tweeted_at
end
end
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[source, ruby]
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# File: vendor/plugins/yaffle/lib/acts_as_yaffle.rb
module Yaffle
def self.included(base)
base.send :extend, ClassMethods
end
module ClassMethods
def acts_as_yaffle(options = {})
cattr_accessor :yaffle_text_field, :yaffle_date_field
self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
self.yaffle_date_field = (options[:yaffle_date_field] || :last_squawked_at).to_s
send :include, InstanceMethods
end
end
module InstanceMethods
def squawk(string)
write_attribute(self.class.yaffle_text_field, string.to_squawk)
write_attribute(self.class.yaffle_date_field, Date.today)
end
end
end
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Note the use of `write_attribute` to write to the field in model.
