function_object

FunctionObject solves a problem of complex² callable¹ objects.

1. By callable I mean something that respond_to? :call. lambda and proc in Ruby are examples of callable objects.
2. By complex I mean something that requires sub-expressions. In other words, complex is when you need to express your call method in terms of other (private) methods. In other words, complex is when you need def inside your lambda or/and need to extract it to separate unit. (So, the explanation of what is complex gone complex too :)

Add this line to your application's Gemfile:

gem 'function_object'

And then execute:

$ bundle

Or install it yourself as:

$ gem install function_object

class Plus < FunctionObject
  args do
    arg :a
    arg :b
  end

  def call
    a + b
  end
end

Plus.call(1,2) # => 3
Plus.(1,2) # => 3

plus = Plus.new(1,2) # => #<Plus:0x00000002115e48 @a=1, @b=2>
plus.() # => 3

Plus.curry.(1).(2) # => 3
Plus.curry.(1,2) # => 3

Or you can define it even simpler:

class Plus < FunctionObject
  args :a, :b

  def call
    a + b
  end
end

Or mix these two styles (not recommended though):

class Plus < FunctionObject
  args :a do
    arg :b
  end

  def call
    a + b
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec 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 tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/marshall-lee/function_object.