method_arguments gem

With the method_arguments gem you can easily set object attributes from method arguments.

Transform this:

  def initialize(user_entity, first_name:, last_name:, email:, phone:, dob:)
    @user_entity = user_entity
    @first_name = first_name
    @last_name = last_name
    @email = email
    @phone = phone
    @dob = dob
  end

into this streamlined version:

  def initialize(user_entity, first_name:, last_name:, email:, phone:, dob:)
    set_instance_vars(__method_args__)
  end

Within any method, call __method_args__ to retrieve its arguments as a Hash.

  def initialize(user_entity, first_name:, last_name:, age:, **kw_rest)
    "Method ##{__method__} received #{__method_args__.inspect} arguments"
  end

1. Argument types *rest and **keyrest are ignored regardless of their name:

   def initialize(arg, *arg_rest, kw_arg:, **kw_rest)
     __method_args__ # returns { a: <value>, kw_arg: <value> }
   end

   Casting unknown arbitrary arguments to instance variables is not recommended for security reasons.

2. The method does not support argument forwarding:

   def self.call(...)
     new(__method_args__).call # raises error
   end

Use set_instance_vars(hash) to assign instance variables from a Hash.

To leverage setters (attribute writers), add use_writers: true argument. If a writer with the corresponding name exists, it will be invoked.

Before:

def initialize(user_entity, first_name:, last_name:, age:)
  @user_entity = user_entity
  @first_name = first_name
  @last_name = last_name
  self.age = age
end

def age=(val)
  @age = Integer(val)
end

After:

def initialize(user_entity, first_name:, last_name:, age:, ...)
  set_instance_vars(__method_args__, use_writers: true)
end

def age=(val)
  @age = Integer(val)
end

1. Add to your Gemfile, then run bundle install:

   gem "method_arguments"

2. Prepend your code with

   require "method_arguments"

This gem is designed to be compatible with Ruby 2.7 and above. It has been tested on the following MRI versions:

• v2.7.2
• v3.0.3
• v3.1.2

If you encounter any issues with later versions, please feel free to report them.