MetaInstance

What Is It?

MetaInstance is a convenient and safe API for accessing and manipulating an object's state.

How Does It Work

MetaInstance adds a method to all objects called #instance. It returns an Instance delegator that provides the full interface to the object's state.

Of course, without implementing this in C, directly in the Ruby source, we are left to depend on the current provisions Ruby has for accessing the state of an object. So there are some limitations here. However, we implement the Ruby code in such a way as to minimize the downsides by caching all the method definitions the Instance class will utilize.

Usage

Let's use a very simple example class with which to demonstrate usage.

    class Song
      attr_accessor :title
      attr_accessor :artist
      attr_accessor :year

      def initialize(title, artist, year)
        @title  = title
        @artist = artist
        @year   = year
      end
    end

Now we can create an instance of Song and work with it's state.

    song = Song.new("Paranoid", "Black Sabbath", 1970)

    song.instance.variables
    # => [:@title, :@artist, :@year]

    song.instance.get(:title)
    # => "Paranoid"

    song.instance[:artist]
    # => "Black Sabbath"

    song.instance.to_h
    # => {:title => "Paranoid", :artist => "Black Sabbath", :year => 1970}

For a more complete set of usage examples see the QED documentation.

Copyrights

BSD-2-Clause License

See LICENSE.txt file for license details.