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class Delegator

Parent:: BasicObject

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 of the use of Delegator:

class SimpleDelegator < Delegator
  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.

Public Class Methods

new(obj) Show source

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

# File lib/delegate.rb, line 71
def initialize(obj)
  __setobj__(obj)
end

Public Instance Methods

!() Show source

Delegates ! to the _getobj_

# File lib/delegate.rb, line 151
def !
  !__getobj__
end

!=(obj) Show source

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

# File lib/delegate.rb, line 143
def !=(obj)
  return false if obj.equal?(self)
  __getobj__ != obj
end

==(obj) Show source

Returns true if two objects are considered of equal value.

# File lib/delegate.rb, line 135
def ==(obj)
  return true if obj.equal?(self)
  self.__getobj__ == obj
end

__getobj__() Show source

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

# File lib/delegate.rb, line 159
def __getobj__
  __raise__ ::NotImplementedError, "need to define `__getobj__'"
end

__raise__()

Alias for: raise

__setobj__(obj) Show source

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

# File lib/delegate.rb, line 167
def __setobj__(obj)
  __raise__ ::NotImplementedError, "need to define `__setobj__'"
end

freeze() Show source

Freeze both the object returned by _getobj_ and self.

# File lib/delegate.rb, line 229

marshal_dump() Show source

Serialization support for the object returned by _getobj_.

# File lib/delegate.rb, line 174
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) Show source

Reinitializes delegation from a serialized object.

# File lib/delegate.rb, line 186
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

method_missing(m, *args, &block) Show source

Handles the magic of delegation through _getobj_.

Calls superclass method BasicObject#method_missing

# File lib/delegate.rb, line 78
def method_missing(m, *args, &block)
  r = true
  target = self.__getobj__ {r = false}

  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
end

methods(all=true) Show source

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

Calls superclass method

# File lib/delegate.rb, line 110
def methods(all=true)
  __getobj__.methods(all) | super
end

protected_methods(all=true) Show source

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

Calls superclass method

# File lib/delegate.rb, line 126
def protected_methods(all=true)
  __getobj__.protected_methods(all) | super
end

public_methods(all=true) Show source

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

Calls superclass method

# File lib/delegate.rb, line 118
def public_methods(all=true)
  __getobj__.public_methods(all) | super
end

raise() Show source

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

# File lib/delegate.rb, line 67

Also aliased as: __raise__

respond_to_missing?(m, include_private) Show source

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

# File lib/delegate.rb, line 95
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() Show source

Taint both the object returned by _getobj_ and self.

# File lib/delegate.rb, line 219

trust() Show source

Trust both the object returned by _getobj_ and self.

# File lib/delegate.rb, line 209

untaint() Show source

Untaint both the object returned by _getobj_ and self.

# File lib/delegate.rb, line 224

untrust() Show source

Untrust both the object returned by _getobj_ and self.

# File lib/delegate.rb, line 214

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Licensed under the Ruby License.
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Licensed under their own licenses.