Class: Delegator (Ruby 2.7.2)
Description: Class : Delegator - Ruby 2.7.2

### Home Classes Methods

### In Files

- delegate.rb
- delegate/version.rb

### Parent

BasicObject

### Methods

- ::new
- #__raise__
- #method_missing
- #raise
- #respond_to_missing?

### Class/Module Index

Quicksearch

- Delegator
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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.

### Constants

KERNEL_RESPOND_TO
VERSION

### 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 71
    def initialize(obj)
      __setobj__(obj)
    end

### Public Instance Methods

__raise__ click to toggle source
Alias for: raise
method_missing(m, *args, &block) click to toggle source

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

      if r && target_respond_to?(target, m, false)
        target.__send__(m, *args, &block)
      elsif ::Kernel.method_defined?(m) || ::Kernel.private_method_defined?(m)
        ::Kernel.instance_method(m).bind_call(self, *args, &block)
      else
        super(m, *args, &block)
      end
    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 67

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 95
    def respond_to_missing?(m, include_private)
      r = true
      target = self.__getobj__ {r = false}
      r &&= target_respond_to?(target, m, include_private)
      if r && include_private && !target_respond_to?(target, m, false)
        warn "delegator does not forward private method \##{m}", uplevel: 3
        return false
      end
      r
    end