PHP之依赖注入容器pimple

原文地址：http://blog.csdn.net/wzllai/article/details/24485245

依赖注入（Dependency Injection）又叫控制反转（Inversion of Control）是一个重要的面向对象编程的法则来削减计算机程序的耦合问题，它能消除组件间的直接依赖关系，让组件的开发更独立，使用更灵活，在java框架中应用非常广泛。在php中由于语言特性不能完全照搬java的那一套，但简单的功能还是可以实现的。pimple就是php社区中比较流行的一种ioc容器。

可以用composer添加 require  "pimple/pimple": "1.*"

pimple的优势是简单，就一个文件

/*
* This file is part of Pimple.
*
* Copyright (c) 2009 Fabien Potencier
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is furnished
* to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

/**
* Pimple main class.
*
* @package pimple
* @author  Fabien Potencier
*/
class Pimple implements \ArrayAccess
{
private $values = array();
private $factories;
private $protected;
private $frozen = array();
private $raw = array();
private $keys = array();

/**
* Instantiate the container.
*
* Objects and parameters can be passed as argument to the constructor.
*
* @param array $values The parameters or objects.
*/
public function __construct(array $values = array())
{
$this->factories = new \SplObjectStorage();
$this->protected = new \SplObjectStorage();

foreach ($values as $key => $value) {
$this->offsetSet($key, $value);
}
}

/**
* Sets a parameter or an object.
*
* Objects must be defined as Closures.
*
* Allowing any PHP callable leads to difficult to debug problems
* as function names (strings) are callable (creating a function with
* the same name as an existing parameter would break your container).
*
* @param  string           $id    The unique identifier for the parameter or object
* @param  mixed            $value The value of the parameter or a closure to define an object
* @throws RuntimeException Prevent override of a frozen service
*/
public function offsetSet($id, $value)
{
if (isset($this->frozen[$id])) {
throw new \RuntimeException(sprintf('Cannot override frozen service "%s".', $id));
}

$this->values[$id] = $value;
$this->keys[$id] = true;
}

/**
* Gets a parameter or an object.
*
* @param string $id The unique identifier for the parameter or object
*
* @return mixed The value of the parameter or an object
*
* @throws InvalidArgumentException if the identifier is not defined
*/
public function offsetGet($id)
{
if (!isset($this->keys[$id])) {
throw new \InvalidArgumentException(sprintf('Identifier "%s" is not defined.', $id));
}

if (
isset($this->raw[$id])
|| !is_object($this->values[$id])
|| isset($this->protected[$this->values[$id]])
|| !method_exists($this->values[$id], '__invoke')
) {
return $this->values[$id];
}

if (isset($this->factories[$this->values[$id]])) {
return $this->values[$id]($this);
}

$this->frozen[$id] = true;
$this->raw[$id] = $this->values[$id];

return $this->values[$id] = $this->values[$id]($this);
}

/**
* Checks if a parameter or an object is set.
*
* @param string $id The unique identifier for the parameter or object
*
* @return Boolean
*/
public function offsetExists($id)
{
return isset($this->keys[$id]);
}

/**
* Unsets a parameter or an object.
*
* @param string $id The unique identifier for the parameter or object
*/
public function offsetUnset($id)
{
if (isset($this->keys[$id])) {
if (is_object($this->values[$id])) {
unset($this->factories[$this->values[$id]], $this->protected[$this->values[$id]]);
}

unset($this->values[$id], $this->frozen[$id], $this->raw[$id], $this->keys[$id]);
}
}

/**
* Marks a callable as being a factory service.
*
* @param callable $callable A service definition to be used as a factory
*
* @return callable The passed callable
*
* @throws InvalidArgumentException Service definition has to be a closure of an invokable object
*/
public function factory($callable)
{
if (!is_object($callable) || !method_exists($callable, '__invoke')) {
throw new \InvalidArgumentException('Service definition is not a Closure or invokable object.');
}

$this->factories->attach($callable);

return $callable;
}

/**
* Protects a callable from being interpreted as a service.
*
* This is useful when you want to store a callable as a parameter.
*
* @param callable $callable A callable to protect from being evaluated
*
* @return callable The passed callable
*
* @throws InvalidArgumentException Service definition has to be a closure of an invokable object
*/
public function protect($callable)
{
if (!is_object($callable) || !method_exists($callable, '__invoke')) {
throw new \InvalidArgumentException('Callable is not a Closure or invokable object.');
}

$this->protected->attach($callable);

return $callable;
}

/**
* Gets a parameter or the closure defining an object.
*
* @param string $id The unique identifier for the parameter or object
*
* @return mixed The value of the parameter or the closure defining an object
*
* @throws InvalidArgumentException if the identifier is not defined
*/
public function raw($id)
{
if (!isset($this->keys[$id])) {
throw new \InvalidArgumentException(sprintf('Identifier "%s" is not defined.', $id));
}

if (isset($this->raw[$id])) {
return $this->raw[$id];
}

return $this->values[$id];
}

/**
* Extends an object definition.
*
* Useful when you want to extend an existing object definition,
* without necessarily loading that object.
*
* @param string   $id       The unique identifier for the object
* @param callable $callable A service definition to extend the original
*
* @return callable The wrapped callable
*
* @throws InvalidArgumentException if the identifier is not defined or not a service definition
*/
public function extend($id, $callable)
{
if (!isset($this->keys[$id])) {
throw new \InvalidArgumentException(sprintf('Identifier "%s" is not defined.', $id));
}

if (!is_object($this->values[$id]) || !method_exists($this->values[$id], '__invoke')) {
throw new \InvalidArgumentException(sprintf('Identifier "%s" does not contain an object definition.', $id));
}

if (!is_object($callable) || !method_exists($callable, '__invoke')) {
throw new \InvalidArgumentException('Extension service definition is not a Closure or invokable object.');
}

$factory = $this->values[$id];

$extended = function ($c) use ($callable, $factory) {
return $callable($factory($c), $c);
};

if (isset($this->factories[$factory])) {
$this->factories->detach($factory);
$this->factories->attach($extended);
}

return $this[$id] = $extended;
}

/**
* Returns all defined value names.
*
* @return array An array of value names
*/
public function keys()
{
return array_keys($this->values);
}
}

pimple类就继承一个php数组对象接口，在程序整个生命周期中，各种属性、方法、对象、闭包都可以注册其中，得易于php的数组的hashtable实现，容器本身的查询效率不算是太低。类似zf1中的Zend_Register或者Yii的委托代理形式，总体来说还是pimple直观些。

pimple只是实现了一个容器的概念，关于依赖注入自动创建关联对象的功能可以参照Laravel4和z2中的实现。一个例子代码:

class A{

}
class B{
public function __construct(A a){}
}
class C{
public function __construct(B b){}
public function dosomething(){}
}
$container = new pimple;

$container->a = function () {
return new A();
};
$c->b = function ($c) {
return new B($c->a);
};
$c->c = function ($c) {
return new C($c->b);
};

// 从容器中取得Foo
$foo = $c->foo;
$foo->doSomething();
// Bim::doSomething|Bar::doSomething|Foo::doSomething
// 依赖注入的核心就是将对象和类的依赖关系注册到容器中。