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class Module
# 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.
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
# 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"
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
end
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