Method: Module#alias_method_chain

Defined in:
lib/core/facets/module/alias_method_chain.rb

#alias_method_chain(target, feature) {|aliased_target, punctuation| ... } ⇒ Object

Encapsulates the common pattern of …

alias_method :foo_without_feature, :foo
alias_method :foo, :foo_with_feature

With this, you simply do …

alias_method_chain :foo, :feature

For example

class AliasMethodChainExample
  def foo 
    "foo"
  end

  def foo_with_feature
    "foo!"
  end

  alias_method_chain :foo, :feature
end

And both aliases are set up for you.

example = AliasMethodChainExample.new
example.foo #=> "foo!"
example.foo_without_feature #=> "foo"

Query and bang methods (foo?, foo!) keep the same punctuation …

alias_method_chain :foo?, :feature

is equivalent to …

alias_method :foo_without_feature?, :foo?
alias_method :foo?, :foo_with_feature?

so you can safely chain foo, foo?, and foo! with the same feature.

CREDIT: Bitsweat, Rails Team

Yields:

  • (aliased_target, punctuation) 


45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/core/facets/module/alias_method_chain.rb', line 45

def alias_method_chain(target, feature)
  # Strip out punctuation on predicates or bang methods since
  # e.g. target?_without_feature is not a valid method name.
  aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1
  yield(aliased_target, punctuation) if block_given?

  with_method, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}"

  alias_method without_method, target
  alias_method target, with_method

  case
    when public_method_defined?(without_method)
      public target
    when protected_method_defined?(without_method)
      protected target
    when private_method_defined?(without_method)
      private target
  end
end