Lantern

# Features

A Feature must contain other Features and/or Actions and should extend Lantern\Features\Feature

<?php

use Lantern\Features\Feature;

class ExampleFeature extends Feature
{
    // optionally override the ID automatically assigned
    const ID = null;
    
    // push your top-level feature onto a different stack
    const STACK = null;

    // An optional description of this feature
    const DESCRIPTION = '';

    const ACTIONS = [
        // declare this features actions here
    ];
    
    const FEATURES = [
        // declare any features attached to this feature here 
    ];
}

Your Feature would then be declared in a parent Feature or in the base AppFeatures Feature (see Setup)


<?php 

use Lantern\Features\Feature;

class AppFeatures extends Feature
{
    const DESCRIPTION = 'Top-level feature';

    const FEATURES = [
        ExampleFeature::class,
    ];
}

# Constraints

If a Feature relies on a system-level dependency, then you can declare this as a constraint.

If any declared constraints of a Feature fail to be met then all of its declared Actions will become unavailable.

# An illustration

Let us say that your app has a Feature that allows a profile picture to be uploaded and resized.

This Feature depends on the convert binary being present on the command line.

Let's say that, during a server migration, a new server is set-up but ImageMagick is not installed and convert is missing.

You're happy everything seems to have moved over well and appears to be working.

# Scenario 1: without Constraints

  1. Some time the next day, you get an email from a customer saying:

    I'm seeing a server error in your app.

  2. You investigate, go back & forth with the customer, trawl through your Laravel logs and realise your mistake.
  3. You rush to fix the problem before more customers get the error.

# Scenario 2: with Constraints

  1. Some time the next day, you get an email from a customer saying:

    I can't find the button to upload my new profile picture.

  2. You know the Constraint has failed, and realise immediately your mistake.
  3. No errors or Exceptions, with a cool head you grab a coffee and set about fixing the problem.

It's a totally different way of handling the same problem, which leaves you looking more professional.

# Declaring Constraints

If your Feature has Constraints to declare, then you must add the following to your class:

protected function constraints(\Lantern\Features\ConstraintsBuilder $constraints) 
{
     //…
}

More info

Please note that constraints can also be declared in your Actions

For info on the available methods of the ConstraintsBuilder see Constraints.

# Multiple Feature graphs

It's possible to work with multiple Feature graphs, thus giving you a way of splitting your Actions into groups.

To do this, simply specify a const STACK = 'my-stack'; onto your top-most Feature.

This has two effects on your application:

  1. You can now have multiple Actions with the same ID, as long as they're in different stacks
  2. When checking authorisation, you must prefix the Action ID with the stack,
    e.g. @can('my-stack.add-todo') … @endcan'

Do not declare a STACK on a sub-feature

If you specify an additional stack on a nested sub-feature, a Lantern\LanternException will be thrown.

← Actions →