Archetype

Simple named library loader for PHP

Archetype provides a generic frontend to resolving implementation classes for a named interface with an extensible plugin architechture.

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Installation

Install via Composer:

composer require decodelabs/archetype

Usage

Importing

Archetype uses Veneer to provide a unified frontage under DecodeLabs\Archetype. You can access all the primary functionality via this static frontage without compromising testing and dependency injection.

Functionality

Use Archetype when designing plugin oriented libraries that need to load arbitrary extension classes based on a naming convention.

By mapping names to classes in an extensible and customisable resolver structure, Archetype allows fast and reliable means to create loosely coupled plugin ecosystems.

Example:

// Main library
namespace My\Library
{

    use DecodeLabs\Archetype;

    interface Thing {}

    class Factory {

        public static function loadThing(string $name): Thing
        {
            // Resolve name to class for Thing interface
            $class = Archetype::resolve(Thing::class, $name);

            return new $class();
        }
    }
}


// Thing implementations
namespace My\Library\Thing
{

    use My\Library\Thing;

    class Box implements Thing {}
    class Potato implements Thing {}
    class Dog implements Thing {}
}



// Calling code
namespace My\App
{

    use My\Library\Factory;

    $box = Factory::loadthing('Box');
    $potato = Factory::loadThing('Potato');
    $dog = Factory::loadThing('Dog');
}

Resolvers

Archetype uses a hierarchy of Resolvers to turn a name into a class. By default, the Handler will fall back on a Resolver\Generic instance that simply locates the named class within the namespace of the associated interface.

In the above example, the implementations of the My\Library\Thing can be found at My\Library\Thing\*.

Custom resolvers

The Resolver\Archetype implementation however will also automatically look for custom Resolver classes in the same location as the target interface, named <Interface>Archetype.

The following example will replace the default functionality and cause Archetype to look in a different location for the Thing implementations:

namespace My\Library {

    use DecodeLabs\Archetype\Resolver;

    class ThingArchetype implements Resolver
    {

        public function getInterface(): string
        {
            return Thing::class;
        }

        public function getPriority(): int
        {
            return 10;
        }

        public function resolve(string $name): ?string
        {
            return 'Some\\Other\\Namespace\\'.$name;
        }
    }
}

Multiple resolvers

Multiple Resolver instances can be stacked against a single interface, called in series based on the priority they request, the first one to return a non-null class name wins.

Alternative Resolvers can be loaded with:

use DecodeLabs\Archetype;
use My\Library\Resolver\Alternative as AlternativeResolver;

Archetype::register(new AlternativeResolver());

File lookup

Resolvers that also implement the Finder interface can define the means to lookup a file path based on the provided name, against the space defined by the target interface.

This can be useful when the space that is defined by the root interface may contain assets aside from PHP code.

It is down to the implementation to decide how to map names to file paths (there are no pre-built default Finder classes).

Example:

namespace My\Library {

    use DecodeLabs\Archetype\Finder;

    class ThingArchetype implements Finder
    {

        public function getInterface(): string
        {
            return Thing::class;
        }

        public function getPriority(): int
        {
            return 10;
        }

        public function resolve(string $name): ?string
        {
            return 'Some\\Other\\Namespace\\'.$name;
        }

        public function findFile(string $name): ?string
        {
            return './some/other/namespace/'.$name.'.jpg';
        }
    }
}


namespace My\App {

    use DecodeLabs\Archetype;
    use My\Library\Thing;

    $boxImagePath = Archetype::findFile(Thing::class, 'box');
}

Licensing

Archetype is licensed under the MIT License. See LICENSE for the full license text.