42 lines
1.4 KiB
Ruby
42 lines
1.4 KiB
Ruby
class Module
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# Provides a delegate class method to easily expose contained objects' methods
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# as your own. Pass one or more methods (specified as symbols or strings)
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# and the name of the target object as the final :to option (also a symbol
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# or string). At least one method and the :to option are required.
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#
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# Delegation is particularly useful with Active Record associations:
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# class Greeter < ActiveRecord::Base
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# def hello() "hello" end
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# def goodbye() "goodbye" end
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# end
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#
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# class Foo < ActiveRecord::Base
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# belongs_to :greeter
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# delegate :hello, :to => :greeter
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# end
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#
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# Foo.new.hello # => "hello"
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# Foo.new.goodbye # => NoMethodError: undefined method `goodbye' for #<Foo:0x1af30c>
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#
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# Multiple delegates to the same target are allowed:
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# class Foo < ActiveRecord::Base
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# delegate :hello, :goodbye, :to => :greeter
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# end
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#
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# Foo.new.goodbye # => "goodbye"
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def delegate(*methods)
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options = methods.pop
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unless options.is_a?(Hash) && to = options[:to]
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raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
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end
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methods.each do |method|
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module_eval(<<-EOS, "(__DELEGATION__)", 1)
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def #{method}(*args, &block)
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#{to}.__send__(#{method.inspect}, *args, &block)
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end
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EOS
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end
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end
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end
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