CODEWITHSUNDEEP
ruby-on-railsmodel-view-controllermodelsolid-principles
Daniel
Daniel

Reputation: 7172

Work flow in MVC models?

I'm looking at the ruby gem workflow: https://github.com/geekq/workflow

The examples and other examples on the web have the workflow code in the model itself. I believe this is a violation of SOLID. Also, business logic would also be encoded in the model class (actions taken as the model goes though several states), which is a violation of the MVC contract.

Example:

class Message

  workflow do
    state :spam_check do
      event :is_spam, transitions_to => :destroy
      event :is_not_spam,:transitions_to => :finished
    end
  end

  # business logic
  def is_spam
    self.user.spammer_score += 1
    if self.user.spammer_score > 5
        self.user.destroy
    end
  end
end

Is this good programming? If not, where in a rails project should state changes be coded?

Upvotes: 1

Views: 397

Answers (2)

bhavik shah
bhavik shah

Reputation: 593

Daniel, it seems that the code listing you shared and the code listing on the Ruby Gem Workflow (https://github.com/geekq/workflow) - define states, events, transitions and actions on the model objects.

Code Listing from the Gem Workflow link

class Article
  include Workflow
  workflow do
    state :new do
      event :submit, :transitions_to => :awaiting_review
    end
    state :awaiting_review do
      event :review, :transitions_to => :being_reviewed
    end
    state :being_reviewed do
      event :accept, :transitions_to => :accepted
      event :reject, :transitions_to => :rejected
    end
    state :accepted
    state :rejected
  end
end

For MVC and SOLID, I think if this code can be modified in such a way that Workflow applies to Controller instead of the Model.

Model is an instance object of domain entities - Message or Article. They don't define workflow themselves. They can be in any state any time. It is the system requirements that has a context of states for any given model objects. For example a message itself doesn't care if its spam. An Article itself does not have a tag that its new, rejected, approved, submitted or being reviewed.

Hence if Controller is given the Workflow responsibilities, then controller will handle events, will take actions and will do state transitions. In that, the actions taken by the controller may perform necessary work to modify model objects.

Real like analogy: Author starts writing article in his notebook (with pen). Keeps it with him till its not satisfactory. The article itself has know meaning that its new / fresh. Then author submits the article for review. The article moves to the reviewer desk, yet Article itself can't define the state that it can't be modified. and so on.

Does that make sense!?

Upvotes: 0

Daniel
Daniel

Reputation: 7172

After some study...

I think that a state diagram represents the state of the model and can easily be abused to be a work flow engine.

Upvotes: 0

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