Class: Delegator

Inherits:
Object
  • Object
show all
Defined in:
lib/delegate.rb

Overview

Delegator is an abstract class used to build delegator pattern objects from subclasses. Subclasses should redefine _getobj_. For a concrete implementation, see SimpleDelegator.

Direct Known Subclasses

SimpleDelegator

Instance Method Summary collapse

Constructor Details

#initialize(obj) ⇒ Delegator Also known as: initialize_methods

Pass in the obj to delegate method calls to. All methods supported by obj will be delegated to.



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# File 'lib/delegate.rb', line 123

def initialize(obj)
  preserved = ::Kernel.public_instance_methods(false)
  preserved -= ["to_s","to_a","inspect","==","=~","==="]
  for t in self.class.ancestors
    preserved |= t.public_instance_methods(false)
    preserved |= t.private_instance_methods(false)
    preserved |= t.protected_instance_methods(false)
    break if t == Delegator
  end
  preserved << "singleton_method_added"
  for method in obj.methods
    next if preserved.include? method
    begin
	eval <<-EOS
 def self.#{method}(*args, &block)
   begin
     __getobj__.__send__(:#{method}, *args, &block)
   rescue Exception
     [email protected]_if{|s| /:in `__getobj__'$/ =~ s} #`
     [email protected]_if{|s| /^\\(eval\\):/ =~ s}
     Kernel::raise
   end
 end
	EOS
    rescue SyntaxError
      raise NameError, "invalid identifier %s" % method, caller(4)
    end
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(m, *args, &block) ⇒ Object

Handles the magic of delegation through _getobj_.



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# File 'lib/delegate.rb', line 155

def method_missing(m, *args, &block)
  target = self.__getobj__
  unless target.respond_to?(m)
    super(m, *args, &block)
  end
  target.__send__(m, *args, &block)
end

Instance Method Details

#__getobj__ ⇒ Object

This method must be overridden by subclasses and should return the object method calls are being delegated to.

Raises:

  • (NotImplementedError) 


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# File 'lib/delegate.rb', line 176

def __getobj__
  raise NotImplementedError, "need to define `__getobj__'"
end

#marshal_dump ⇒ Object

Serialization support for the object returned by _getobj_.



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# File 'lib/delegate.rb', line 181

def marshal_dump
  __getobj__
end

#marshal_load(obj) ⇒ Object

Reinitializes delegation from a serialized object.



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# File 'lib/delegate.rb', line 185

def marshal_load(obj)
  initialize_methods(obj)
  __setobj__(obj)
end

#respond_to?(m, include_private = false) ⇒ Boolean

Checks for a method provided by this the delegate object by fowarding the call through _getobj_.

Returns:

  • (Boolean) 


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# File 'lib/delegate.rb', line 167

def respond_to?(m, include_private = false)
  return true if super
  return self.__getobj__.respond_to?(m, include_private)
end