ChangesValidator

ChangesValidator is the most minimalistic state machine implementation focused on validating a state changes rather than define API methods and logic.

The best way to define API and logic in Ruby is using Ruby. ChangesValidator does only validation that Object can move from one state to another.

ActiveModel

Add this line to your application's Gemfile:

gem 'changes_validator'

And then execute:

$ bundle

If the state machine's main goal is to validate changess than let's implement it as a validation:

class Reward < AR::Base
  validates! :state, :changes => { 
    nil => [:pending], # Initial state is always pending
    :pending => [:approved, :rejected], # Pending can be changed to to approved and rejected
    :approved => :paid # Approved can only be changed to paid
  }
end

Recommended to use with strict validation method: validates! as wrong state changes use to be programmer mistake but not user input mistake. In this case exception will be raise and logged.

• :message - validation message. Can have %{value} and %{old_value} interpolation variables.
  • Default: "Can not be changed to %{value}"
  • Example: "Can not be changed from %{old_value} to %{value}"
• :allow_nil - don't apply validator if value is nil
• :allow_blank - don't apply validator if value is blank
• :if - only apply validator if specified method return true
• :unless - only apply validator if specified method return false
• :strict - if true this validator will always raise when record is invalid
  • Default:

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request