method

delegate_missing_to

v5.1.7 - Show latest stable - 0 notes - Class: Module

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What's this?

delegate_missing_to(target) public

When building decorators, a common pattern may emerge:

class Partition
  def initialize(first_event)
    @events = [ first_event ]
  end

  def people
    if @events.first.detail.people.any?
      @events.collect { |e| Array(e.detail.people) }.flatten.uniq
    else
      @events.collect(&:creator).uniq
    end
  end

  private
    def respond_to_missing?(name, include_private = false)
      @events.respond_to?(name, include_private)
    end

    def method_missing(method, *args, &block)
      @events.send(method, *args, &block)
    end
end

With `Module#delegate_missing_to`, the above is condensed to:

class Partition
  delegate_missing_to :@events

  def initialize(first_event)
    @events = [ first_event ]
  end

  def people
    if @events.first.detail.people.any?
      @events.collect { |e| Array(e.detail.people) }.flatten.uniq
    else
      @events.collect(&:creator).uniq
    end
  end
end

The target can be anything callable within the object. E.g. instance variables, methods, constants and the likes.

Show source

# File activesupport/lib/active_support/core_ext/module/delegation.rb, line 264
  def delegate_missing_to(target)
    target = target.to_s
    target = "self.#{target}" if DELEGATION_RESERVED_METHOD_NAMES.include?(target)

    module_eval       def respond_to_missing?(name, include_private = false)        # It may look like an oversight, but we deliberately do not pass        # +include_private+, because they do not get delegated.        #{target}.respond_to?(name) || super      end      def method_missing(method, *args, &block)        if #{target}.respond_to?(method)          #{target}.public_send(method, *args, &block)        else          super        end      end, __FILE__, __LINE__ + 1
  end

delegate_missing_to

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