In Ruby, new operator does not guarantee, for sure, that you can mass-assign instance variables. And when you want to do that, you should have known you should not writing the code by hand, over and over again.

Assignbot guarantee that you can mass-assign variables from .assign. Furthermore, implementing Assignbot does not require massive code changes to your codebase, unless you want custom behaviour.

1. Assign from the hash, from params
2. Assign from the hash, from JSON

To install Assignbot, add this line to your Gemfile:

gem 'assignbot'

And then execute:

$ bundle

Or install it system-wide by issuing:

$ gem install assignbot

Assume you have the following User class:

class User
  attr_accessor :name, :age, :id
end

Basic usage of assigner does not require significant code change to your model/ruby class, other than a one-liner include statement:

class User
  include Assignbot

  # your other ruby code
end

By doing so, you already make User to be assignable from a Hash:

user_params = {
  name: "Adam Pahlevi",
  age: 23,
  id: "934-2311"
}

user = User.new
user.assign(user_params)
user.name == "Adam Pahlevi" # returns true

If you would like to explicitly tell Assignbot what are the assignable variables, then you have to define the variables explicitly:

class User
  include Assignbot

  assigner do
    name from: :name
    age from: :age
    id from: :id
  end
  # your other ruby code
end

Explicitly defining assigner also allow you to map the value from source variable, which have different nomenclature, to the target variable in your Ruby class.

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