php ioc 实现

PHP IoC 实现方法

依赖注入容器

依赖注入（DI）是IoC的核心实现方式之一。通过容器管理对象的依赖关系，避免硬编码依赖。

class Container {
    protected $instances = [];

    public function bind($abstract, $concrete = null) {
        if (is_null($concrete)) {
            $concrete = $abstract;
        }
        $this->instances[$abstract] = $concrete;
    }

    public function make($abstract, $parameters = []) {
        if (!isset($this->instances[$abstract])) {
            $this->bind($abstract);
        }
        return $this->resolve($this->instances[$abstract], $parameters);
    }

    protected function resolve($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 new $concrete;
        }
        $dependencies = $constructor->getParameters();
        $instances = $this->resolveDependencies($dependencies);
        return $reflector->newInstanceArgs($instances);
    }

    protected function resolveDependencies($parameters) {
        $dependencies = [];
        foreach ($parameters as $parameter) {
            $dependency = $parameter->getClass();
            if (is_null($dependency)) {
                if ($parameter->isDefaultValueAvailable()) {
                    $dependencies[] = $parameter->getDefaultValue();
                } else {
                    throw new Exception("Cannot resolve dependency {$parameter->name}");
                }
            } else {
                $dependencies[] = $this->make($dependency->name);
            }
        }
        return $dependencies;
    }
}

服务定位器模式

服务定位器是另一种实现IoC的方式，通过中央注册表获取服务实例。

class ServiceLocator {
    private $services = [];
    private $instantiated = [];

    public function register(string $name, callable $resolver) {
        $this->services[$name] = $resolver;
    }

    public function has(string $name): bool {
        return isset($this->services[$name]);
    }

    public function get(string $name) {
        if (!isset($this->instantiated[$name])) {
            $this->instantiated[$name] = $this->services[$name]();
        }
        return $this->instantiated[$name];
    }
}

接口绑定实现

通过接口绑定具体实现，实现松耦合。

interface LoggerInterface {
    public function log(string $message);
}

class FileLogger implements LoggerInterface {
    public function log(string $message) {
        file_put_contents('log.txt', $message, FILE_APPEND);
    }
}

$container = new Container();
$container->bind(LoggerInterface::class, FileLogger::class);
$logger = $container->make(LoggerInterface::class);

自动装配实现

利用反射自动解析依赖关系，减少手动配置。

class AutoWiringContainer extends Container {
    public function make($abstract, $parameters = []) {
        if (!isset($this->instances[$abstract])) {
            $this->bind($abstract);
        }
        return parent::make($abstract, $parameters);
    }
}

实际应用示例

展示如何在MVC框架中使用IoC容器。

class UserController {
    private $userRepository;

    public function __construct(UserRepository $userRepository) {
        $this->userRepository = $userRepository;
    }
}

$container = new Container();
$container->bind(UserRepository::class, DatabaseUserRepository::class);
$controller = $container->make(UserController::class);

以上实现方法展示了PHP中IoC容器的核心概念和不同实现方式，从基础的依赖注入到自动装配，可以根据项目需求选择适合的方案。