Method argument constraints

Gem for setting constraints on method arguments. Very similar to contracts but a bit simpler. It also does not validate the return of method.

• It leverages classes already existing in your project when validating when doing direct comparison (more to come on this later)
• It allows you to define customized constraints easily when what you want to do is a bit atypical ie pass a proc or define a method in your class and pass the name as a symbol

Add this line to your application's Gemfile:

gem 'method_argument_constraints'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install method_argument_constraints

To set requirements based on an already existing class you'd do it like so:

class A
  def hi(friend)
  method_constraints!(binding, friend: String)
    puts "hi #{friend}"
  end
end

If the kind of constraint isn't as straightforward as just a is_a? comparison you could do it one of two other ways

class A
  def hi(number)
  my_proc = Proc.new{|arg_value, _arg_name| arg_value.is_a? Integer && arg_value > 1 }
  method_constraints!(binding, friend: my_proc)
    puts "number: #{number}"
  end
end

or

class A
  def my_validation_method(arg_value, _arg_name)
    arg_value.is_a? Integer && arg_value > 1
  end

  def hi(number)
  method_constraints!(binding, friend: :my_validation_method)
    puts "number: #{number}"
  end
end

Note that: When using a Proc or method the return value must always be a boolean value

Why do we need to pass the current binding? This allows the gem to access the arguments, and parameters the method we want to validate was called with.

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/etsenake/method_argument_constraints. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

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

Everyone interacting in this project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.