前言
首先欢迎关注我的博客：
在前面几个博客中，我详细讲了 Ioc 容器各个功能的使用、绑定的源码、解析的源码，今天这篇博客会详细介绍 Ioc 容器的一些细节，一些特性，以便更好地掌握容器的功能。
注：本文使用的测试类与测试对象都取自 laravel 的单元测试文件src/illuminate/tests/Container/ContainerTest.php
rebind绑定特性
rebind 在绑定之前
instance 和 普通 bind 绑定一样，当重新绑定的时候都会调用 rebind 回调函数，但是有趣的是，对于普通 bind 绑定来说，rebind 回调函数被调用的条件是当前接口被解析过：
public function testReboundListeners(){ unset($_SERVER['__test.rebind']); $container = new Container; $container->rebinding('foo', function () { $_SERVER['__test.rebind'] = true; }); $container->bind('foo', function () { }); $container->make('foo'); $container->bind('foo', function () { }); $this->assertTrue($_SERVER['__test.rebind']);} 所以遇到下面这样的情况,rebinding 的回调函数是不会调用的：
public function testReboundListeners(){ unset($_SERVER['__test.rebind']); $container = new Container; $container->rebinding('foo', function () { $_SERVER['__test.rebind'] = true; }); $container->bind('foo', function () { }); $container->bind('foo', function () { }); $this->assertFalse(isset($_SERVER['__test.rebind']));} 有趣的是对于 instance 绑定：
public function testReboundListeners(){ unset($_SERVER['__test.rebind']); $container = new Container; $container->rebinding('foo', function () { $_SERVER['__test.rebind'] = true; }); $container->bind('foo', function () { }); $container->instance('foo', function () { }); $this->assertTrue(isset($_SERVER['__test.rebind']));} rebinding 回调函数却是可以被调用的。其实原因就是 instance 源码中 rebinding 回调函数调用的条件是 rebound 为真，而普通 bind 函数调用 rebinding 回调函数的条件是 resolved 为真. 目前笔者不是很清楚为什么要对 instance 和 bind 区别对待，希望有大牛指导。
rebind 在绑定之后
为了使得 rebind 回调函数在下一次的绑定中被激活，在 rebind 函数的源码中，如果判断当前对象已经绑定过，那么将会立即解析：
public function rebinding($abstract, Closure $callback){ $this->reboundCallbacks[$abstract = $this->getAlias($abstract)][] = $callback; if ($this->bound($abstract)) { return $this->make($abstract); }} 单元测试代码：
public function testReboundListeners1(){ unset($_SERVER['__test.rebind']); $container = new Container; $container->bind('foo', function () { return 'foo'; }); $container->resolving('foo', function () { $_SERVER['__test.rebind'] = true; }); $container->rebinding('foo', function ($container,$object) {//会立即解析 $container['foobar'] = $object.'bar'; }); $this->assertTrue($_SERVER['__test.rebind']); $container->bind('foo', function () { }); $this->assertEquals('bar', $container['foobar']);} resolving 特性
resolving 回调的类型
resolving 不仅可以针对接口执行回调函数，还可以针对接口实现的类型进行回调函数。
public function testResolvingCallbacksAreCalledForType(){ $container = new Container; $container->resolving('StdClass', function ($object) { return $object->name = 'taylor'; }); $container->bind('foo', function () { return new StdClass; }); $instance = $container->make('foo'); $this->assertEquals('taylor', $instance->name);}public function testResolvingCallbacksShouldBeFiredWhenCalledWithAliases(){ $container = new Container; $container->alias('StdClass', 'std'); $container->resolving('std', function ($object) { return $object->name = 'taylor'; }); $container->bind('foo', function () { return new StdClass; }); $instance = $container->make('foo'); $this->assertEquals('taylor', $instance->name);} resolving 回调与 instance
前面讲过，对于 singleton 绑定来说，resolving 回调函数仅仅运行一次，只在 singleton 第一次解析的时候才会调用。如果我们利用 instance 直接绑定类的对象，不需要解析，那么 resolving 回调函数将不会被调用：
public function testResolvingCallbacksAreCalledForSpecificAbstracts(){ $container = new Container; $container->resolving('foo', function ($object) { return $object->name = 'taylor'; }); $obj = new StdClass; $container->instance('foo', $obj); $instance = $container->make('foo'); $this->assertFalse(isset($instance->name));} extend 扩展特性
extend 用于扩展绑定对象的功能，对于普通绑定来说，这个函数的位置很灵活：
在绑定前扩展
public function testExtendIsLazyInitialized(){ ContainerLazyExtendStub::$initialized = false; $container = new Container; $container->extend('Illuminate\Tests\Container\ContainerLazyExtendStub', function ($obj, $container) { $obj->init(); return $obj; }); $container->bind('Illuminate\Tests\Container\ContainerLazyExtendStub'); $this->assertFalse(ContainerLazyExtendStub::$initialized); $container->make('Illuminate\Tests\Container\ContainerLazyExtendStub'); $this->assertTrue(ContainerLazyExtendStub::$initialized);} 在绑定后解析前扩展
public function testExtendIsLazyInitialized(){ ContainerLazyExtendStub::$initialized = false; $container = new Container; $container->bind('Illuminate\Tests\Container\ContainerLazyExtendStub'); $container->extend('Illuminate\Tests\Container\ContainerLazyExtendStub', function ($obj, $container) { $obj->init(); return $obj; }); $this->assertFalse(ContainerLazyExtendStub::$initialized); $container->make('Illuminate\Tests\Container\ContainerLazyExtendStub'); $this->assertTrue(ContainerLazyExtendStub::$initialized);} 在解析后扩展
public function testExtendIsLazyInitialized(){ ContainerLazyExtendStub::$initialized = false; $container = new Container; $container->bind('Illuminate\Tests\Container\ContainerLazyExtendStub'); $container->make('Illuminate\Tests\Container\ContainerLazyExtendStub'); $this->assertFalse(ContainerLazyExtendStub::$initialized); $container->extend('Illuminate\Tests\Container\ContainerLazyExtendStub', function ($obj, $container) { $obj->init(); return $obj; }); $this->assertFalse(ContainerLazyExtendStub::$initialized); $container->make('Illuminate\Tests\Container\ContainerLazyExtendStub'); $this->assertTrue(ContainerLazyExtendStub::$initialized);} 可以看出，无论在哪个位置，extend 扩展都有 lazy 初始化的特点，也就是使用 extend 函数并不会立即起作用，而是要等到 make 解析才会激活。
extend 与 instance 绑定
对于 instance 绑定来说，暂时 extend 的位置需要位于 instance 之后才会起作用，并且会立即起作用，没有 lazy 的特点：
public function testExtendInstancesArePreserved(){ $container = new Container; $obj = new StdClass; $obj->foo = 'foo'; $container->instance('foo', $obj); $container->extend('foo', function ($obj, $container) { $obj->bar = 'baz'; return $obj; }); $this->assertEquals('foo', $container->make('foo')->foo); $this->assertEquals('baz', $container->make('foo')->bar);} extend 绑定与 rebind 回调
无论扩展对象是 instance 绑定还是 bind 绑定，extend 都会启动 rebind 回调函数：
public function testExtendReBindingInstance(){ $_SERVER['_test_rebind'] = false; $container = new Container; $container->rebinding('foo',function (){ $_SERVER['_test_rebind'] = true; }); $obj = new StdClass; $container->instance('foo',$obj); $container->make('foo'); $container->extend('foo', function ($obj, $container) { return $obj; }); this->assertTrue($_SERVER['_test_rebind']);}public function testExtendReBinding(){ $_SERVER['_test_rebind'] = false; $container = new Container; $container->rebinding('foo',function (){ $_SERVER['_test_rebind'] = true; }); $container->bind('foo',function (){ $obj = new StdClass; return $obj; }); $container->make('foo'); $container->extend('foo', function ($obj, $container) { return $obj; }); this->assertFalse($_SERVER['_test_rebind']);} contextual 绑定特性
contextual 在绑定前
contextual 绑定不仅可以与 bind 绑定合作，相互不干扰，还可以与 instance 绑定相互合作。而且 instance 的位置也很灵活，可以在 contextual 绑定前，也可以在contextual 绑定后：
public function testContextualBindingWorksForExistingInstancedBindings(){ $container = new Container; $container->instance('Illuminate\Tests\Container\IContainerContractStub', new ContainerImplementationStub); $container->when('Illuminate\Tests\Container\ContainerTestContextInjectOne')->needs('Illuminate\Tests\Container\IContainerContractStub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl );} contextual 在绑定后
public function testContextualBindingWorksForNewlyInstancedBindings(){ $container = new Container; $container->when('Illuminate\Tests\Container\ContainerTestContextInjectOne')->needs('Illuminate\Tests\Container\IContainerContractStub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $container->instance('Illuminate\Tests\Container\IContainerContractStub', new ContainerImplementationStub); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl );} contextual 绑定与别名
contextual 绑定也可以在别名上进行，无论赋予别名的位置是 contextual 的前面还是后面：
public function testContextualBindingDoesntOverrideNonContextualResolution(){ $container = new Container; $container->instance('stub', new ContainerImplementationStub); $container->alias('stub', 'Illuminate\Tests\Container\IContainerContractStub'); $container->when('Illuminate\Tests\Container\ContainerTestContextInjectTwo')->needs('Illuminate\Tests\Container\IContainerContractStub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectTwo')->impl ); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStub', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl );}public function testContextualBindingWorksOnNewAliasedBindings(){ $container = new Container; $container->when('Illuminate\Tests\Container\ContainerTestContextInjectOne')->needs('Illuminate\Tests\Container\IContainerContractStub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $container->bind('stub', ContainerImplementationStub::class); $container->alias('stub', 'Illuminate\Tests\Container\IContainerContractStub'); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl );} 争议
目前比较有争议的是下面的情况：
public function testContextualBindingWorksOnExistingAliasedInstances(){ $container = new Container; $container->alias('Illuminate\Tests\Container\IContainerContractStub', 'stub'); $container->instance('stub', new ContainerImplementationStub); $container->when('Illuminate\Tests\Container\ContainerTestContextInjectOne')->needs('stub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl ); } 由于instance的特性，当别名被绑定到其他对象上时，别名 stub 已经失去了与 IlluminateTestsContainerIContainerContractStub 之间的关系，因此不能使用 stub 代替作上下文绑定。
但是另一方面：public function testContextualBindingWorksOnBoundAlias(){ $container = new Container; $container->alias('Illuminate\Tests\Container\IContainerContractStub', 'stub'); $container->bind('stub', ContainerImplementationStub::class); $container->when('Illuminate\Tests\Container\ContainerTestContextInjectOne')->needs('stub')->give('Illuminate\Tests\Container\ContainerImplementationStubTwo'); $this->assertInstanceOf( 'Illuminate\Tests\Container\ContainerImplementationStubTwo', $container->make('Illuminate\Tests\Container\ContainerTestContextInjectOne')->impl ); } 代码只是从 instance 绑定改为 bind 绑定，由于 bind 绑定只切断了别名中的 alias 数组的联系，并没有断绝abstractAlias数组的联系，因此这段代码却可以通过，很让人难以理解。本人在给 Taylor Otwell 提出 PR 时，作者原话为“I'm not making any of these changes to the container on a patch release.”。也许，在以后(5.5或以后)版本作者会更新这里的逻辑，我们就可以看看服务容器对别名绑定的态度了，大家也最好不要这样用。
服务容器中的闭包函数参数
服务容器中很多函数都有闭包函数，这些闭包函数可以放入特定的参数，在绑定或者解析过程中，这些参数会被服务容器自动带入各种类对象或者服务容器实例。
bind 闭包参数
public function testAliasesWithArrayOfParameters(){ $container = new Container; $container->bind('foo', function ($app, $config) { return $config; }); $container->alias('foo', 'baz'); $this->assertEquals([1, 2, 3], $container->makeWith('baz', [1, 2, 3]));} extend 闭包参数
public function testExtendedBindings(){ $container = new Container; $container['foo'] = 'foo’; $container->extend('foo', function ($old, $container) { return $old.'bar’; }); $this->assertEquals('foobar', $container->make('foo')); $container = new Container; $container->singleton('foo', function () { return (object) ['name' => 'taylor']; }); $container->extend('foo', function ($old, $container) { $old->age = 26; return $old; }); $result = $container->make('foo'); $this->assertEquals('taylor', $result->name); $this->assertEquals(26, $result->age); $this->assertSame($result, $container->make('foo'));} bindmethod 闭包参数
public function testCallWithBoundMethod(){ $container = new Container; $container->bindMethod('Illuminate\Tests\Container\ContainerTestCallStub@unresolvable', function ($stub,$container) { $container['foo'] = 'foo'; return $stub->unresolvable('foo', 'bar'); }); $result = $container->call('Illuminate\Tests\Container\ContainerTestCallStub@unresolvable'); $this->assertEquals(['foo', 'bar'], $result); $this->assertEquals('foo',$container['foo']);} resolve 闭包参数
public function testResolvingCallbacksAreCalledForSpecificAbstracts(){ $container = new Container; $container->resolving('foo', function ($object，$container) { return $object->name = 'taylor'; }); $container->bind('foo', function () { return new StdClass; }); $instance = $container->make('foo'); $this->assertEquals('taylor', $instance->name);} rebinding 闭包参数
public function testReboundListeners(){ $container = new Container; $container->bind('foo', function () { return 'foo'; }); $container->rebinding('foo', function ($container,$object) { $container['bar'] = $object.'bar'; }); $container->bind('foo', function () { }); $this->assertEquals('bar',$container['foobar']);}