Class: Module

Inherits:
Object
  • Object
show all
Defined in:
lib/aliasing.rb,
lib/attribute_accessors.rb

Overview

:nodoc:

Instance Method Summary collapse

Instance Method Details

#alias_attribute(new_name, old_name) ⇒ Object

Allows you to make aliases for attributes, which includes getter, setter, and query methods.

Example:

class Content < ActiveRecord::Base
  # has a title attribute
end

class Email < ActiveRecord::Base
  alias_attribute :subject, :title
end

e = Email.find(1)
e.title    # => "Superstars"
e.subject  # => "Superstars"
e.subject? # => true
e.subject = "Megastars"
e.title    # => "Megastars"



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# File 'lib/aliasing.rb', line 81

def alias_attribute(new_name, old_name)
  module_eval <<-STR, __FILE__, __LINE__+1
    def #{new_name}; #{old_name}; end
    def #{new_name}?; #{old_name}?; end
    def #{new_name}=(v); self.#{old_name} = v; end
  STR
end

#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

And both aliases are set up for you.

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.

Yields:

  • (aliased_target, punctuation) 


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# File 'lib/aliasing.rb', line 53

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?
  alias_method "#{aliased_target}_without_#{feature}#{punctuation}", target
  alias_method target, "#{aliased_target}_with_#{feature}#{punctuation}"
end

#mattr_accessor(*syms) ⇒ Object 



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# File 'lib/attribute_accessors.rb', line 75

def mattr_accessor(*syms)
  mattr_reader(*syms)
  mattr_writer(*syms)
end

#mattr_reader(*syms) ⇒ Object 



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# File 'lib/attribute_accessors.rb', line 35

def mattr_reader(*syms)
  syms.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end
    
      def self.#{sym}
        @@#{sym}
      end

      def #{sym}
        @@#{sym}
      end
    EOS
  end
end

#mattr_writer(*syms) ⇒ Object 



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# File 'lib/attribute_accessors.rb', line 54

def mattr_writer(*syms)
  options = syms.last.is_a?(Hash) ? syms.pop : {}
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end
    
      def self.#{sym}=(obj)
        @@#{sym} = obj
      end
    
      #{"
      def #{sym}=(obj)
        @@#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end