Class: Delegator

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses: SimpleDelegator
Inherits:	BasicObject
Defined in:	lib/delegate.rb

Overview

This library provides three different ways to delegate method calls to an object. The easiest to use is ::SimpleDelegator. Pass an object to the constructor and all methods supported by the object will be delegated. This object can be changed later.

Going a step further, the top level #DelegateClass method allows you to easily setup delegation through class inheritance. This is considerably more flexible and thus probably the most common use for this library.

Finally, if you need full control over the delegation scheme, you can inherit from the abstract class Delegator and customize as needed. (If you find yourself needing this control, have a look at Forwardable which is also in the standard library. It may suit your needs better.)

SimpleDelegator's implementation serves as a nice example if the use of Delegator:

class SimpleDelegator < Delegator
  def initialize(obj)
    super                  # pass obj to Delegator constructor, required
    @delegate_sd_obj = obj # store obj for future use
  end

  def __getobj__
    @delegate_sd_obj # return object we are delegating to, required
  end

  def __setobj__(obj)
    @delegate_sd_obj = obj # change delegation object,
                           # a feature we're providing
  end
end

Notes

Be advised, RDoc will not detect delegated methods.

Class Method Summary

.new(obj) ⇒ Delegator constructor

Pass in the obj to delegate method calls to.

Instance Method Summary

#!

Delegates ! to the _getobj_.
#!=(obj)

Returns true if two objects are not considered of equal value.
#==(obj)

Returns true if two objects are considered of equal value.
#__getobj__

This method must be overridden by subclasses and should return the object method calls are being delegated to.
#__setobj__(obj)

This method must be overridden by subclasses and change the object delegate to obj.
#freeze

Freeze both the object returned by _getobj_ and self.
#marshal_dump

Serialization support for the object returned by _getobj_.
#marshal_load(data)

Reinitializes delegation from a serialized object.
#method_missing(m, *args, &block)

Handles the magic of delegation through _getobj_.
#methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ methods.
#protected_methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ protected methods.
#public_methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ public methods.
#raise

Use __raise__ if your Delegator does not have a object to delegate the raise method call.
#respond_to_missing?(m, include_private) ⇒ Boolean

Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
#taint

Taint both the object returned by _getobj_ and self.
#trust

Trust both the object returned by _getobj_ and self.
#untaint

Untaint both the object returned by _getobj_ and self.
#untrust

Untrust both the object returned by _getobj_ and self.

Constructor Details

.new(obj) ⇒ `Delegator`

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

[ GitHub ]

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


def initialize(obj)
  __setobj__(obj)
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(m, *args, &block)

Handles the magic of delegation through _getobj_.

[ GitHub ]

# File 'lib/delegate.rb', line 82


def method_missing(m, *args, &block)
  r = true
  target = self.__getobj__ {r = false}
  begin
    if r && target.respond_to?(m)
      target.__send__(m, *args, &block)
    elsif ::Kernel.respond_to?(m, true)
      ::Kernel.instance_method(m).bind(self).(*args, &block)
    else
      super(m, *args, &block)
    end
  ensure
    $@.delete_if {|t| %r"\A#{Regexp.quote(__FILE__)}:(?:#{[__LINE__-7, __LINE__-5, __LINE__-3].join('|')}):"o =~ t} if $@
  end
end

Instance Method Details

#!

Delegates ! to the _getobj_

[ GitHub ]

# File 'lib/delegate.rb', line 158


def !
  !__getobj__
end

#!=(obj)

Returns true if two objects are not considered of equal value.

[ GitHub ]

# File 'lib/delegate.rb', line 150


def !=(obj)
  return false if obj.equal?(self)
  __getobj__ != obj
end

#==(obj)

Returns true if two objects are considered of equal value.

[ GitHub ]

# File 'lib/delegate.rb', line 142


def ==(obj)
  return true if obj.equal?(self)
  self.__getobj__ == obj
end

#getobj

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

[ GitHub ]

# File 'lib/delegate.rb', line 166


def __getobj__
  __raise__ ::NotImplementedError, "need to define `__getobj__'"
end

#setobj(obj)

This method must be overridden by subclasses and change the object delegate to obj.

[ GitHub ]

# File 'lib/delegate.rb', line 174


def __setobj__(obj)
  __raise__ ::NotImplementedError, "need to define `__setobj__'"
end

#freeze

Freeze both the object returned by _getobj_ and self.

[ GitHub ]

# File 'lib/delegate.rb', line 237


rdoc_method :method: freeze

#marshal_dump

Serialization support for the object returned by _getobj_.

[ GitHub ]

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


def marshal_dump
  ivars = instance_variables.reject {|var| /\A@delegate_/ =~ var}
  [
    :__v2__,
    ivars, ivars.map{|var| instance_variable_get(var)},
    __getobj__
  ]
end

#marshal_load(data)

Reinitializes delegation from a serialized object.

[ GitHub ]

# File 'lib/delegate.rb', line 193


def marshal_load(data)
  version, vars, values, obj = data
  if version == :__v2__
    vars.each_with_index{|var, i| instance_variable_set(var, values[i])}
    __setobj__(obj)
  else
    __setobj__(data)
  end
end

#methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ methods.

[ GitHub ]

# File 'lib/delegate.rb', line 117


def methods(all=true)
  __getobj__.methods(all) | super
end

#protected_methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ protected methods.

[ GitHub ]

# File 'lib/delegate.rb', line 133


def protected_methods(all=true)
  __getobj__.protected_methods(all) | super
end

#public_methods(all = true)

Returns the methods available to this delegate object as the union of this object's and _getobj_ public methods.

[ GitHub ]

# File 'lib/delegate.rb', line 125


def public_methods(all=true)
  __getobj__.public_methods(all) | super
end

#raise

Use __raise__ if your Delegator does not have a object to delegate the raise method call.

[ GitHub ]

# File 'lib/delegate.rb', line 66


rdoc_method :method: raise

#respond_to_missing?(m, include_private) ⇒ `Boolean`

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

[ GitHub ]

# File 'lib/delegate.rb', line 102


def respond_to_missing?(m, include_private)
  r = true
  target = self.__getobj__ {r = false}
  r &&= target.respond_to?(m, include_private)
  if r && include_private && !target.respond_to?(m, false)
    warn "#{caller(3)[0]}: delegator does not forward private method \##{m}"
    return false
  end
  r
end

#taint

Taint both the object returned by _getobj_ and self.

[ GitHub ]

# File 'lib/delegate.rb', line 222


rdoc_method :method: taint

#trust

Trust both the object returned by _getobj_ and self.

[ GitHub ]

# File 'lib/delegate.rb', line 212


rdoc_method :method: trust

#untaint

Untaint both the object returned by _getobj_ and self.

[ GitHub ]

# File 'lib/delegate.rb', line 227


rdoc_method :method: untaint

#untrust

Untrust both the object returned by _getobj_ and self.

[ GitHub ]

# File 'lib/delegate.rb', line 217


rdoc_method :method: untrust

Class: Delegator

Overview

Notes

Class Method Summary

Instance Method Summary

Constructor Details

.new(obj) ⇒ Delegator

Dynamic Method Handling

#method_missing(m, *args, &block)

Instance Method Details

#!

#!=(obj)

#==(obj)

#__getobj__

#__setobj__(obj)

#freeze

#marshal_dump

#marshal_load(data)

#methods(all = true)

#protected_methods(all = true)

#public_methods(all = true)

#raise

#respond_to_missing?(m, include_private) ⇒ Boolean

#taint

#trust

#untaint

#untrust

.new(obj) ⇒ `Delegator`

#getobj

#setobj(obj)

#respond_to_missing?(m, include_private) ⇒ `Boolean`