PHP依赖倒置(Dependency Injection)代码实例

<?php
?
class Container
{
??? protected $setings = array();
?
??? public function set($abstract,$concrete = null)
??? {
??????? if ($concrete === null) {
??????????? $concrete = $abstract;
??????? }
?
??????? $this->setings[$abstract] = $concrete;
??? }
?
??? public function get($abstract,$parameters = array())
??? {
??????? if (!isset($this->setings[$abstract])) {
??????????? return null;
??????? }
?
??????? return $this->build($this->setings[$abstract],$parameters);
??? }
?
??? public function build($concrete,$parameters)
??? {
??????? if ($concrete instanceof Closure) {
??????????? return $concrete($this,$parameters);
??????? }
?
??????? $reflector = new ReflectionClass($concrete);
?
??????? if (!$reflector->isInstantiable()) {
??????????? throw new Exception("Class {$concrete} is not instantiable");
??????? }
?
??????? $constructor = $reflector->getConstructor();
?
??????? if (is_null($constructor)) {
??????????? return $reflector->newInstance();
??????? }
?
??????? $parameters = $constructor->getParameters();
??????? $dependencies = $this->getDependencies($parameters);
?
??????? return $reflector->newInstanceArgs($dependencies);
??? }
?
??? public function getDependencies($parameters)
??? {
??????? $dependencies = array();
??????? foreach ($parameters as $parameter) {
??????????? $dependency = $parameter->getClass();
??????????? if ($dependency === null) {
??????????????? if ($parameter->isDefaultValueAvailable()) {
??????????????????? $dependencies[] = $parameter->getDefaultValue();
??????????????? } else {
??????????????????? throw new Exception("Can not be resolve class dependency {$parameter->name}");
??????????????? }
??????????? } else {
??????????????? $dependencies[] = $this->get($dependency->name);
??????????? }
??????? }
?
??????? return $dependencies;
??? }
}

<必修php
?
require 'container.php';
?
?
interface MyInterface{}
class Foo implements MyInterface{}
class Bar implements MyInterface{}
class Baz
{
??? public function __construct(MyInterface $foo)
??? {
??????? $this->foo = $foo;
??? }
}
?
$container = new Container();
$container->set('Baz','Baz');
$container->set('MyInterface','Foo');
$baz = $container->get('Baz');
print_r($baz);
$container->set('MyInterface','Bar');
$baz = $container->get('Baz');
print_r($baz);