Class: Delegator (Ruby 2.3.2)
Description: Class : Delegator - Ruby 2.3.2

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Support for the Ruby 2.3 series has ended. See here for reference.

### Home Classes Methods

### In Files

- delegate.rb

### Parent

BasicObject

### Methods

- ::new
- #!
- #!=
- #==
- #__getobj__
- #__raise__
- #__setobj__
- #freeze
- #marshal_dump
- #marshal_load
- #method_missing
- #methods
- #protected_methods
- #public_methods
- #raise
- #respond_to_missing?
- #taint
- #trust
- #untaint
- #untrust

### Class/Module Index

Quicksearch

- Delegator
- Object
- SimpleDelegator

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# Delegator

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) click to toggle source

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

                   # File delegate.rb, line 70
    def initialize(obj)
      __setobj__(obj)
    end

### Public Instance Methods

!() click to toggle source

Delegates ! to the _getobj_

                   # File delegate.rb, line 150
    def !
      !__getobj__
    end

!=(obj) click to toggle source

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

                   # File delegate.rb, line 142
    def !=(obj)
      return false if obj.equal?(self)
      __getobj__ != obj
    end

==(obj) click to toggle source

Returns true if two objects are considered of equal value.

                   # File delegate.rb, line 134
    def ==(obj)
      return true if obj.equal?(self)
      self.__getobj__ == obj
    end

__getobj__() click to toggle source

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

                   # File delegate.rb, line 158
    def __getobj__
      __raise__ ::NotImplementedError, "need to define `__getobj__'"
    end

__raise__ click to toggle source
Alias for: raise
__setobj__(obj) click to toggle source

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

                   # File delegate.rb, line 166
    def __setobj__(obj)
      __raise__ ::NotImplementedError, "need to define `__setobj__'"
    end

freeze click to toggle source

Freeze both the object returned by _getobj_ and self.

                   # File delegate.rb, line 228

marshal_dump() click to toggle source

Serialization support for the object returned by _getobj_.

                   # File delegate.rb, line 173
    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) click to toggle source

Reinitializes delegation from a serialized object.

                   # File delegate.rb, line 185
    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) click to toggle source

Handles the magic of delegation through _getobj_.

                   # File delegate.rb, line 77
    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) click to toggle source

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

                   # File delegate.rb, line 109
    def methods(all=true)
      __getobj__.methods(all) | super
    end

protected_methods(all=true) click to toggle source

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

                   # File delegate.rb, line 125
    def protected_methods(all=true)
      __getobj__.protected_methods(all) | super
    end

public_methods(all=true) click to toggle source

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

                   # File delegate.rb, line 117
    def public_methods(all=true)
      __getobj__.public_methods(all) | super
    end

raise click to toggle source

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

                   # File delegate.rb, line 66

Also aliased as: __raise__
respond_to_missing?(m, include_private) click to toggle source

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

                   # File delegate.rb, line 94
    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 click to toggle source

Taint both the object returned by _getobj_ and self.

                   # File delegate.rb, line 218

trust click to toggle source

Trust both the object returned by _getobj_ and self.

                   # File delegate.rb, line 208

untaint click to toggle source

Untaint both the object returned by _getobj_ and self.

                   # File delegate.rb, line 223

untrust click to toggle source

Untrust both the object returned by _getobj_ and self.

                   # File delegate.rb, line 213