Moist::Action

This module provides validation logic for controller actions. You can use it to replace strong params in Rails and simplify testing.

Add this line to your application's Gemfile:

gem 'moist-action'

And then execute:

$ bundle

Or install it yourself as:

$ gem install moist-action

Each action should be extracted to separate class:

class RegisterUser
  include Moist::Action
  
  params do
    required(:name).filled(:str?)
    required(:email).filled(format?: EMAIL_REGEX)
    required(:age).maybe(:int?)
  end

  def perform(params)
    User.create(params)
  end
end

You are free and strongly encouraged to use class constructor to inject buisenes logic. The idiomatic way to use Moist::Action is to validate user input and call buisenes logic.

class RegisterUser
  include Moist::Action
  
  def initialize(users_service:)
    @users_service = users_service   
  end
  
  params do
    required(:name).filled(:str?)
    required(:email).filled(format?: EMAIL_REGEX)
    required(:age).maybe(:int?)
  end

  def perform(params)
    @users_service.register(params)
  end
end

Method perform considered private and should never be called directly. Use call method instead. It validates user input and call perform passing filtered hash.

action = RegisterUser.new(users_service: users_service)
action.(params)

Method params receive only three valid params (name, email, and age). Any additional params will be stripped out. It doesn't call perform at all if params are invalid.
Moist::Action uses dry-validation under the hood.

The result of evaluation of call method is either Fear::Left (with errors hash) in case of invalid params or Fear::Reght (with result of evaluation of perform method) in case of valid params

action.(email: 'CarlLazlo@example.com', age: 39) #=> Fear::Left({ name: ['must be filled'] }) 
action.(name: 'Carl Lazlo', email: 'CarlLazlo@example.com', age: 39) #=> Fear::Right(User)

You can define what to do in case of validation success of failure:

result = register.(params)
result.reduce(
  ->(errors) { render_unprocessable_entity(errors) },
  ->(user) { render_json(user) }
)

Either monad has rich api, see docs for details.

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/moist-rb/action.