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Dependency injection container

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Table of contents

Installation

composer require weew/container

Creating a container

The container has no additional dependencies, so a simple instantiation will do the trick.

$container = new Container();

Primitive data

Storing any type of data:

$container->set('foo', 'bar');

// returns bar
$container->get('foo');

Classes

Retrieving classes:

class Foo {}

// returns a new instance of Foo
$container->get(Foo::class);

Passing additional parameters:

class Foo {
    public function __construct($x, $y = 2) {};
}

// parameters are matched by name
$container->get(Foo::class, ['x' => 1]);

Resolving constructor dependencies:

class Foo {
    public function __construct(Bar $bar) {}
}
class Bar {}

// returns a new instance of Foo,
// Foo's constructor receives a new instance of Bar
$container->get(Foo::class);

Sharing a specific instance:

class Foo {}

$container->set(Foo::class, new Foo());
// or
$container->set(new Foo());

// everyone will get the same instance of Foo
$container->get(Foo::class);

Factories

Working with factories:

class Foo {
    public $bar;
}
class Bar {}

// a factory method will get it's dependencies resolved too.
$container->set(Foo::class, function(Bar $bar) {
    $foo = new Foo();
    $foo->bar = $bar;

    return $foo;
});

Accessing container from within a factory:

$container->set('foo', 1);

// a container can be injected the same way as any other dependency
$container->set('bar', function(IContainer $container) {
    return $container->get('foo');
));

Container is not limited to closure factories, it supports class method and static method factories too:

class MyFactoryClass {
    public function factoryMethod(AnotherDependency $dependency) {}
    public function staticFactoryMethod(AnotherDependency $dependency) {}
}

$container->set(Foo::class, new MyFactoryClass(), 'factoryMethod');
$container->set(Foo::class, MyFactoryClass::class, 'factoryMethod');
$container->set(Foo::class, MyFactoryClass::class, 'staticFactoryMethod');

Traditional callable array syntax is also supported. It does exactly the same as the examples above, but with a slightly different syntax:

$container->set(Foo::class, [new MyFactoryClass(), 'factoryMethod']);
$container->set(Foo::class, [MyFactoryClass::class, 'factoryMethod']);
$container->set(Foo::class, [MyFactoryClass::class, 'staticFactoryMethod']);

All facotires benefit from dependency injection. Additionaly, if you let the container instantiate your factory, it will be resolved trough the container too.

Interfaces

Resolving interfaces:

interface IFoo {}
class Foo implements IFoo {}

$container->set(IFoo::class, Foo::class);

// will return an instance of Foo
$container->get(IFoo::class);

Sharing specific interface implementation:

interface IFoo {}
class Foo implements IFoo {}

$container->set(IFoo::class, new Foo());

// everyone will get the same instance of Foo
$container->get(IFoo::class);

Interfaces can have factories too:

interface IFoo {}
class Foo implements IFoo {}

$container->set(IFoo::class, function() {
    return new Foo();
});

// will return a new instance of Foo
$container->get(IFoo::class);

Of course you can also type hint interfaces:

interface IFoo {}
class Foo implements IFoo {}
class Bar {
    public function __construct(IFoo $foo) {}
}

$container->set(IFoo::class, Foo::class);

// returns an instance of Bar
// Bar receives an instance of Foo, which implements the interface IFoo
$container->get(Bar::class);

Functions and methods

Functions can get resolved by the container:

class Bar {}
function foo(Bar $bar, $foo) {}

// method foo gets called and receives an instance of Bar
// as with the other container methods, you can always pass your own arguments
$container->callFunction('foo', ['foo' => 1]);

The same works for closures:

class Bar {}

// closure gets called and receives an instance of Bar
$container->callFunction(function(Bar $bar) {});

Invoking class methods is also strait forward:

class Foo {}
class Bar {
    public function takeFoo(Foo $foo, $x) {}
}

$bar = new Bar();
// method takeFoo gets invoked and receives a new instance
// of Foo, as well as the custom arguments
$container->callMethod($bar, 'takeFoo', ['x' => 1]);
// you could also let the container create an instance
$container->callMethod(Bar::class, 'takeFoo', ['x' => 1]);

Invoking static methods:

class Foo {}
class Bar {
    public static function takeFoo(Foo $foo, $x) {}
}

// method takeFoo gets invoked and receives a new instance
// of Foo, as well as the custom arguments
$container->callStaticMethod(Bar::class, 'takeFoo', ['x' => 1]);

It is possible to use PHP's traditional callable syntax for invocation of functions and methods:

// same as $container->callFunction($functionName, $args)
$container->call($functionName, $args);
// same as $container->callFunction($closure, $args)
$container->call($closure, $args);
// same as $container->callMethod($instance, $method, $args)
$container->call([$instance, $method], $args);
// same as $container->callMethod($className, $method, $args)
$container->call([$className, $method], $args);
// same as $container->callStaticMethod($className, $staticMethod, $args)
$container->call([$className, $staticMethod], $args);

Singletons

Container values can be defined as singletons. A singleton definition will return the same value over and over again. Here is an example of a singleton interface definition:

interface IFoo {}
class Foo implements IFoo {}

$container->set(IFoo::class, Foo::class)->singleton();

The same works for classes:

class Foo {}

$container->set(Foo::class)->singleton();

And factories:

class Foo {}

$container->set(Foo::class, function() {
    return new Foo();
})->singleton();

Sharing an instance always results in a singleton:

class Foo {}

$container->set(Foo::class, new Foo())->singleton();
// same as
$container->set(Foo::class, new Foo());

Wildcards

This one might be especially useful when working with factories. Lets take Doctrine for example. You can not simply instantiate a repository by yourself. But still, it would be great if you could have them resolved by the container. Unfortunately, this will throw an error, since the repository requires a special parameter that can and should not be resolved by the container:

class MyRepository {
    public function __construct(SpecialUnresolvableValue $value) {}
}

$container->get(MyRepository::class);

However, you might use a wildcard factory. You can use any regex pattern as a mask. Right now, the only supported regex delimiters are / and #.

class MyRepository implements IRepository {
    public function __construct(SpecialUnresolvableValue $value) {}
}
class YoursRepository implements IRepository {
    public function __construct(SpecialUnresolvableValue $value) {}
}

$container->set('/Repository$/', function(RepositoryFactory $factory, $abstract) {
    return $factory->createRepository($abstract);
});

$container->get(MyRepository::class);
$container->get(YourRepository::class);

As you see here, the actual class name MyRepository was passed to the custom factory as the $abstract parameter. From there, we call the RepositoryFactory and tell it to create us a new instance of MyRepository. Afterwards the same factory can be used to create an instance of YourRepository.

Telling the container that all instances produced within this factory should be singletons is very simple:

$container->set('/Repository$/', function(RepositoryFactory $factory, $abstract) {
    return $factory->createRepository($abstract);
})->singleton();

Wildcards are very powerful, however, they should be used with caution, since they could break your application if you configure them wrong. (for example: if the regex mask is not precise enough and matches unwanted classes). Thanks to regex, creating precise masks shouldn't be a big deal though.

Wildcards can also be used in combination of class names and instances. But I find the usecases for this very limited:

$container->set('/Repository$/', EntityRepository::class);
$container->set('/Repository$/', $instance);

Aliases

If you need to create an alias for a definition, for example when you want to provide a factory for a class as well as for it's interface, and don't want to do it twice for each one, you could create a definition with an alias (or two, or ten). Just provide an array of identifiers. The first element in the array is considered as "the id" and the others are aliases.

$container->set([MyImplementation::class, IImplementation::class], function() {
    return new MyImplementation('foo');
});

// both calls will return a value from the same factory
$container->get(MyImplementation::class);
$container->get(IImplementation::class);

The same would work with singletons, primitive values and so on.

Additional methods

Check if the container has a value:

$container->set('foo', 'bar');

// will return true
$container->has('foo');

Remove a value from the container:

$container->set('foo', 'bar');
$container->remove('foo');

// will return false
$container->has('foo');

Extensions

There are additional extension available to make the container even more powerful.

Doctrine integration

The weew/container-doctrine-integration package makes doctrine repositories injectable.

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