A dynamic dependency injection manager

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Language: PHP

v0.1.0 2014-01-08 20:34 UTC

README

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This library provides a class to handle dependency injection dynamically.

Dynamic dependency injection means you don't have to define services or define which dependencies needs to be injected. The dependencies is dynamically created based on the constructor parameters.

This means you only need to add type-hints for the classes you want to inject into your class constructor.

Installation

Composer

To install this library using composer, add the following to your composer.json:

{
    "require": {
        "pierredup/di": "*"
    }
}

Make sure you are using composer's autoloader to include the file:

require 'vendor/autoload.php';

Download the file

Download Di.phar from the repo and save the file into your project path somewhere.

require 'path/to/Di.phar';

Usage

Getting a class with dependencies

namespace Foo {

    class Bar
    {
        public function __construct(Baz $baz)
        {
            // ...
        }
    }

    class Baz {

    }
}

$object = Di::get('Foo\Bar');

var_dump($object);

This will give you an instance of Foo\Bar with the Baz class dynamically created and injection into the constructor.

Getting a new instance of a class

By default, the same instance for each class will be returned every time you call Di::get If you want to return a new instance of a class, you need to pass a second parameter to the get method

    $object = Di::get('Foo\Bar', Di::NEW_INSTANCE);

This will return a new instance of the Foo\Bar class, but the dependencies will always return the same instance.

If you want to ensure that every object returns a new instance, you need to pass the Di::DEEP flag:

    $object = Di::get('Foo\Bar', Di::DEEP);

This will return a new instance of Foo\Bar, as well as new instances for each dependency.

Parameters

Setting parameters

If you have values in your constructor that can not be type-hinted by an object ( E.G database settings), you use can use the map method to set the values for those parameters:

class Db
{
    public function __construct($host, $username, $password)
    {
        // ...
    }
}

Di::map(array(
    'host'      => 'localhost',
    'username'  => 'user',
    'host'      => 'password',
));

$object = Di::get('Db');

Note: If you don't specify a value for a parameter that doesn't have a type-hint, NULL will be passed as the value. If you set a default value for the parameter, then the default value will be used instead.

Lazy loading parameters

If you want parameters to be lazy-loaded (only load when needed, E.G get value from a database or a session ), you can use a closure or valid callback as the parameter:

Di::map(array(
    'parameter' => function() {
        return Di::get('Foo\Database')->getValueFromDb()
    }
));

// OR

Di::map(array(
    'parameter' => array($db, 'getValueFromDb')
));

The function or callback will only be executed when the parameter is needed, and the value will then be cached for any further calls.

Getting parameters

To get a parameter value, just pass the Di::PARAM flag to the get method:

Di::map(array(
    'host'      => 'localhost',
    'username'  => 'user',
    'host'      => 'password',
));

$host = Di::get('host', Di::PARAM); // return 'localhost'
Over writing classes

You can also use the map method to over write a class name. This is useful if you want to over write a core class of a library with your own implementation. Note that your class needs to extend from the class you are over writing, otherwise you might get an error or unexpected results.

namespace Foo {
    class Bar
    {

    }
}

namespace Baz {
    use Foo\Bar;

    class FooBar extends Bar
    {

    }
}

Di::map(array(
    'Foo\Bar' => 'Baz\FooBar'
));

$object = Di::get('Foo\Bar'); // will return an instance of `Baz\FooBar`

TODO

  • Setter Injection #1
  • Cache class instances #2
  • Define services #3
  • Map interface to concrete class #4