Alternatives to alias_method_chain

gistfile1.rb

# Different ways to hook into an action

class ExampleAPI
  def foo
    puts "Foo"
  end
end

# Option 1: alias_method_chain
class ExampleAPI

  alias_method_chain :foo, :bar

  def foo_with_bar
     foo_without_bar
     puts "did foo"
  end

end

# Pros:
# * gets the job done if there isn't an API
#
# Cons:
# * Makes code flow insane.
# * Brittle.
# * You get away with not defining an API.

# Option 2: Subclass

class SubclassThisAPI
  def foo
    puts "foo"
  end
end

class MySubclass < SubclassThisAPI
  def foo
    super
    puts "Did foo"
  end
end

# Pro:
# * Override APIs without public APIs. Sane backtrace.
#
# Con:
# * You can only hook into public methods
# * Subclass bloat

# Option 3: Explicitely declare an API, through blocks

class BlockPoweredAPI
   attr_accesor :afterFoo
   def foo
    if afterFoo
       afterFoo.call(self)
    end
    puts "foo"
   end
end

@blockpowered = BlockPoweredAPI.new
@blockpowered.afterFoo = {|api| puts "Just did foo" }

# Pro:
# * Well defined API
# * No subclass bloat
# Con:
# * Can't unit test blocks. Have to test at the unit test level.
# * Blocks are closures. Be careful.

class DelegatePoweredAPI
  attr_accessor :delegate
  def foo
    puts "foo"
    if delegate
      delegate.didFoo(self)
    end
  end
end

class MyDelegate
  def didFoo(api)
    puts "Did foo."
  end
end

@delegateAPI = DelegatePoweredAPI.new
@delegateAPI.delegate = MyDelegate.new

# Pro:
# * One class could act as a delegate to multiple classes
# * You can unit test the delegate
# Con:
# * Requires more setup than blocks.
# * Less common in Ruby