Automatically create scopes for all available state_machine states in Rails 3.1

contact.rb

class Contact < ActiveRecord::Base
  
  state_machine :state, :initial => :imported do
    state :imported
    state :contacted
    state :verified
    state :prospect
    state :deleted
  end

  include StateMachineScopes
  state_machine_scopes :state

end

state_machine_scopes.rb

module StateMachineScopes
  class MethodAlreadyDefinedError < StandardError; end
  class StateMachineNotFoundError < StandardError; end
  class NoStateMachineNotFoundError < StandardError; end

  module ClassMethods
    def all_states(machine = :state)
      machine = machine.to_sym
      if state_machines.key?(machine)
        state_machines[machine.to_sym].states.keys.compact.sort
      else
        raise StateMachineNotFoundError.new(%Q{"#{self.name}" does not seem to have a state machine called "#{machine}".})
      end
    end

    def state_machine_scopes(*which)
      options = which.last.is_a?(Hash) ? which.pop : {}
      prefix = options.delete(:prefix)

      if which.any?
        which.each do |machine_name|
          define_scopes_for(machine_name, prefix)
        end
      else
        state_machines.keys.each do |machine_name|
          define_scopes_for(machine_name, prefix)
        end
      end
    end

  private

    def define_scopes_for(machine_name, prefix)
      state_machines[machine_name.to_sym].states.keys.compact.each do |state|
        scope_name = [prefix, machine_name, state].compact.join('_')
        debugger if scope_name.to_s == 'state'
        if self.respond_to? scope_name
          raise MethodAlreadyDefinedError.new("Already defined method called \"#{scope_name}\"")
        end
        self.class_eval do
          scope :"#{scope_name}", where(:state => state)
        end
      end
    end

  end

  def self.included(klass)
    if klass.respond_to?(:state_machines)
      klass.extend(ClassMethods)
    else
      raise NoStateMachineNotFoundError.new(%Q{"#{klass.name}" does not seem to have any state machines.})
    end
  end

end

state_machine_scopes_spec.rb

require 'spec_helper'

describe StateMachineScopes do

  class TestBase
    class << self
      def where(*args); end

      def scope(name, *args)
        scopes << name
      end

      def scopes
        @scopes ||= []
        @scopes
      end
    end
  end

  before :each do
    class ClassWithStateMachine < TestBase
      state_machine do
        state :initialized
        state :ready
      end
    end

    class ClassWithNamedStateMachine < TestBase
      state_machine :mystatus do
        state :initialized
        state :ready
      end
    end

    class ClassWithMultipleStateMachine < TestBase
      state_machine :hello do
        state :world
        state :endofworld
      end

      state_machine :mystatus do
        state :initialized
        state :ready
      end
    end
  end

  after :each do
    Object.send(:remove_const, :ClassWithStateMachine)
    Object.send(:remove_const, :ClassWithNamedStateMachine)
    Object.send(:remove_const, :ClassWithMultipleStateMachine)
  end

  context "inclusion" do
    it "throws error if no state machines are found" do
      expect do
        Class.new.send :include, StateMachineScopes
      end.to raise_error(StateMachineScopes::NoStateMachineNotFoundError)
    end

    class ClassWithStateMachineMethod
      class << self
        def state_machines; end
      end
    end

    it "should have state_machine_scope method" do
      ClassWithStateMachineMethod.send :include, StateMachineScopes
      ClassWithStateMachineMethod.should respond_to(:state_machine_scopes)
    end
  end

  context "build state machine scopes" do

    context "all states" do
      it "finds all states for default state machine name" do
        ClassWithStateMachine.send :include, StateMachineScopes
        ClassWithStateMachine.all_states.should eql  [:initialized, :ready]
      end

      it "finds all states for specific state machine name" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        ClassWithMultipleStateMachine.all_states(:hello).should eql [:endofworld, :world]
      end

      it "throws error if state machine is not defined" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        expect do
          ClassWithMultipleStateMachine.all_states(:dostuff)
        end.to raise_error(StateMachineScopes::StateMachineNotFoundError)

      end
    end

    context "without arguments" do
      it "for default state machine name" do
        ClassWithStateMachine.send :include, StateMachineScopes
        ClassWithStateMachine.state_machine_scopes
        ClassWithStateMachine.scopes.should eql [:state_initialized, :state_ready]
      end

      it "for named state machine" do
        ClassWithNamedStateMachine.send :include, StateMachineScopes
        ClassWithNamedStateMachine.state_machine_scopes
        ClassWithNamedStateMachine.scopes.should eql [:mystatus_initialized, :mystatus_ready]
      end
    end

    context "with arguments" do
      it "only specified state machines" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        ClassWithMultipleStateMachine.state_machine_scopes(:hello)
        ClassWithMultipleStateMachine.scopes.should eql [:hello_world, :hello_endofworld]
      end

      it "adds prefix" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        ClassWithMultipleStateMachine.state_machine_scopes(:prefix => :test)
        ClassWithMultipleStateMachine.scopes.should eql [:test_hello_world, :test_hello_endofworld, :test_mystatus_initialized, :test_mystatus_ready]
      end

      it "ignored other options" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        ClassWithMultipleStateMachine.state_machine_scopes(:foo => :bar)
        ClassWithMultipleStateMachine.scopes.should eql [:hello_world, :hello_endofworld, :mystatus_initialized, :mystatus_ready]
      end

      it "adds prefix and creates only for specified state machines" do
        ClassWithMultipleStateMachine.send :include, StateMachineScopes
        ClassWithMultipleStateMachine.state_machine_scopes(:hello, :prefix => 'test')
        ClassWithMultipleStateMachine.scopes.should eql [:test_hello_world, :test_hello_endofworld]
      end
    end

  end

end

glad you found use for it :)

So great! Thanks for sharing. Looks like on line 41:

 #state_machine_scopes.rb
           scope :"#{scope_name}", where(:state => state)

Should be:

          scope :"#{scope_name}", where(machine_name => state)

(My machine uses :status)