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

Features

1. Reading Method Arguments

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

Limitations

1. Argument types `*rest` and `**keyrest` are ignored regardless of their name:
 
  ```ruby
  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](https://docs.ruby-lang.org/en/3.2/syntax/methods_rdoc.html#label-Argument+Forwarding):

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

2. Filling instance @variables

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

3. Filling instance @variables using attribute writers

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

Example

Before:

```ruby
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:

```ruby
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
```

Installation

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

   gem "method_arguments"
   

2. Prepend your code with

   require "method_arguments"
   

Supported Ruby Versions

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.