Get transitionable states from state on Model

[bjrnblm]

It would be nice to get allowedTransitions from the current state in a model with HasStates enabled so we can use that to fill for example a dropdown in a form.

Example code:

Article.php

protected function registerStates(): void
{
    $this
        ->addState('state', ArticleState::class)
        ->default(Concept::class)
        ->allowTransitions([
            [Concept::class, SubmittedForApproval::class],
            [Concept::class, Cancelled::class],
        ]);
}

Code:

$article = Article::first();
return $article->getAllowedTransitionsFrom('state', Concept::class);

Result:

[
  "App\\States\\SubmittedForApproval",
  "App\\States\\Cancelled"
]

Improvements

Not completely happy with the end result, would prefer it if:

$allowedTransitionsFrom[] = get_class($this->stateClass::make($to, $model));

Could be:

$allowedTransitionsFrom[] = $this->stateClass::make($to, $model);

So we get the transition classes instead of a string and we can do stuff like:

$allowedTransitions = $article->getAllowedTransitionsFrom('state', Concept::class);
foreach($allowedTransitions as $transition){
    dump((string) $transition, get_class($transition));
}

However I cannot get the tests to work that way, mainly because in HasStates the method getStateConfig is private.
So I am not sure how to load it from the Payment model inside the test.

Any input on this?

[brendt]

Could you give an example of when it would be useful to know the allowed transitions?

[bjrnblm]

I have a system where people in an organisation can propose articles for their blog and assign these to different people in this organisation. An article goes through multiple states before it gets published on the blog, for example:

Concept -> Submitted For Approval -> Rejected -> Submitted For Approval -> Approved -> Published

On the edit page of an article I would like to get the allowed states from the current state:

public function edit(Request $request, Article $article) : Renderable
{
    $allowedTransitions = $article->getAllowedTransitionsFrom('state', $article->state);

    return view('articles.edit')
        ->with('article', $article)
        ->with('allowedTransitions', $allowedTransitions);
}

So in articles/edit.blade.php I can render a select box with the allowed transitions for current state:

<select id="state" name="state">
    <option value="">Don't change</option>
    @foreach($allowedTransitions as $transition)
        <option value="{{ $transition }}">{{ $transition }}</option>
    @endforeach
</select>

So for an article in "Concept" stage, the correct options are showed:

[brendt]

I'm ok with adding this. Please check my review, also don't forget to add docs for this feature in the docs folder.

[brendt]

Thanks for all the changes! One more question, would it be possible to also allow this?

$transitionableStates = $payment->state->transitionableStates();

[bjrnblm]

I agree, that would be a nicer syntax to use. I will look into it the coming days.

[brendt]

Thank you very much. Great PR up until now!

[brendt]

It's unfortunate that we'd have to do $payment->state->transitionableStates('fieldName');, in practice fieldName will always be the name of the property it's called upon. I have an idea to fix this though: we can resolve the state config when constructing a state, giving us access to the field name:

    public function __construct(Model $model)
    {
        $this->model = $model;
        
        $this->stateConfig = $model::getStateConfig()[get_parent_class($this)];
    }

Than the transitionableStates on the state class could be refactored to

public function transitionableStates(): array
{
    return $this->model->transitionableStates(get_class($this), $this->stateConfig->field);
}

There are some issues with this approach still (an infinite loop for one), but I believe these could be solved. @bjrnblm if you're not up for it, feel free to let me know, I'll be happy to merge your PR in as is (after you made the last changes I requested), and I'll give it a go myself.

[brendt]

Scratch that, it wouldn't work. I made a wrong assumption

[bjrnblm]

@brendt Yes, I was also struggling with this today. The state does not know to which key it is assigned to in the getStateConfig array of the model.

For now I copied your code from the transitionTo method, but with the nullable $field + reset() it doesn't feel like a proper solution.

Tried to work around this but got stuck on several occasions, so it seems like a good idea to fix the docblocks etc and look at the problem later with a fresh mind.

[bjrnblm]

Hi @brendt anything I can do for this to PR to get it merged?

[brendt]

Oh sorry, I lost track of this one. I'll do my best to merge it later today!

[Hyra]

Ooh, this looks like a great addition! 👏

[brendt]

Thanks again, sorry for the delay. It's released as 1.3.0: https://github.com/spatie/laravel-model-states/releases/tag/1.3.0