Similar to the Laravel's Event and Listener system, the Fraction hook system allows you to execute actions in sequence, much like the concept of a pipeline. For this, you should call the then method after registering an action.

Here is an example of a full pipeline for:

1. Creating a user
2. Sending welcome email
3. Enabling free trial of a product
4. Send account ready notification

We start by defining the actions that will create the user, without any then hook:

// app/Actions/Users.php

execute('create user', function (array $data) {
    return User::create($data);
});

Then, we define the action that will send welcome email. Here we set the then hook to call the next action in the pipeline, which is enabling free trial:

// app/Actions/Emails.php

use App\Models\User;

execute('send welcome user email', function (User $user) {
    // ...
})->then('enable free trial');

After that, we define the action that will enable free trial, and for this action, we set another then hook to call the next action in the pipeline, which is send account ready notification:

// app/Actions/Products.php

use Illuminate\Http\Request;

execute('enable free trial', function (User $user) {
    // ...
})->then('send account ready notification');

Finally, we define the action that will perform the last step of your _pipeline, send a user account ready notification. Since this is the last action in the pipeline, we do not set any then hook:

// app/Actions/Notifications.php

use Illuminate\Http\Request;

execute('send account ready notification', function (User $user) {
    // ...
});

Now you should run the first action of the pipeline: send welcome user email.

namespace App\Http\Controllers;

use Illuminate\Http\Request\CreateUserRequest;

class UserController extends Controller
{
    public function store(CreateUserRequest $request)
    {
        // ...

        $user = run('create user', $request->validated());

        run('send welcome user email', $user);
    }
}

Although the above example uses generic names, you can choose to use a name that makes it easier for you to understand, such as: new user pipeline. Also, we only used "sync actions" in the above scenario, but you are completely free to use the then hook on actions of type deferred or queued.

Shared Arguments

You may have noticed that from the send welcome user email action onwards the \App\Models\User $user argument is repeated in the other actions, right? This happens because all the arguments sent to an action are passed to the others using the hook then system.

Undetected Loop

By default, the only loop Fraction detected is the attempt to call the then hook for the same function that defines it. Nothing is stopping you from creating a ping-pong effect; that's up to you, but make no mistake: you can create an infinite loop with this, so be careful!