ApplicationAction = ActiveModel::Attributes + Kind::Result

application_action_sample.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  gem 'kind', git: 'https://github.com/serradura/kind', branch: 'main', require: false

  gem 'activemodel', require: 'active_model'
end

require 'kind'
require 'kind/result'
require 'kind/validator'

class ApplicationAction
  include ActiveModel::Model
  include ActiveModel::Attributes
  include Kind::Result::Methods

  attribute :id

  def self.call(input = nil)
    new( Kind::Hash.empty_or(input) ).call
  end

  def self.to_proc
    ->(action) { ->(input) { action.call(input) } }.(self)
  end

  def call
    raise NotImplementedError
  end
end

class User
  attr_reader :id, :name

  def self.find_by(id:)
    new(id, 'John Doe') if id
  end

  def initialize(id, name)
    @id = id
    @name = name
  end

  def update(params)
    !!Kind::Try.presence(params[:name], :strip) { |name| @name = name }
  end

  def errors
    OpenStruct.new(full_messages: ["Name can't be blank"])
  end
end

class User
  Find = ->(arg) do
    input = Kind::Hash.empty_or(arg)

    user = ::User.find_by(id: input[:id])

    return Kind::Success(input.merge(user: user)) if user

    Kind::Failure(message: "user not found")
  end
end

class User::Update < ApplicationAction
  attribute :user
  attribute :user_params

  validates :user, kind: User
  validates :user_params, kind: Hash

  def call
    return Failure(errors: self.errors) if invalid?

    return Success(:user_updated, user: user) if user.update(user_params)

    return Failure(:user_cant_be_updated, user: user)
  end
end

result =
  {id: 1, user_params: { name: 'Serradura' }}
    .then(&User::Find)
    .then(&User::Update)

p result
# #<Kind::Success type=:user_updated value={:user=>#<User:0x00007ff8133d9d58 @id=1, @name="Serradura">}>