IvarEquatable

This Ruby gem which adds a module which when included to a class enables its instances to be compared based on their instance variables.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add ivar_equatable

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install ivar_equatable

Usage

Include the IvarEquatable module in your class to make its instances capable of comparing themselves with the == and eql? methods.

In order for two objects to be equal, they've got to have the same instance variables, and the values stored in them have to return true when compared using the == operator.

class MyClass
    include IvarEquatable

    attr_accessor :foo, :bar

    def initialize(foo: nil, bar: nil)
        @foo = foo
        @bar = bar
    end
end

obj1 = MyClass.new foo: :some_value
obj2 = MyClass.new foo: :some_value
obj1 == obj2 #=> true

obj1 = MyClass.new foo: :some_value
obj2 = MyClass.new foo: :other_value
obj1 == obj2 #=> false

obj1 = MyClass.new foo: :some_value
obj2 = MyClass.new foo: :some_value, bar: 2
obj1 == obj2 #=> false

obj1 = MyClass.new foo: { some: { nested: [:hash, :and, :array] } }
obj2 = MyClass.new foo: { some: { nested: [:hash, :and, :array] } }
obj1 == obj2 #=> true

obj1 = MyClass.new foo: { some: { nested: [:hash, :and, :array] } }
obj2 = MyClass.new foo: { some: { nested: :different } }
obj1 == obj2 #=> false

# works on subclasses
class ChildClass < MyClass; end

obj1 = MyClass.new foo: :some_value
obj2 = ChildClass.new foo: :some_value
obj1 == obj2 #=> true

# comparing instances of unrelated classes always returns `false`
class NonRelatedClass
    include IvarEquatable

    attr_accessor :foo, :bar

    def initialize(foo: nil, bar: nil)
        @foo = foo
        @bar = bar
    end
end

obj1 = MyClass.new foo: :some_value
obj2 = NonRelatedClass.new foo: :some_value
obj1 == obj2 #=> false

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Verseth/ivar_equatable.

License

The gem is available as open source under the terms of the MIT License.