Laravel 框架三种绑定 bind、singleton、instance 源码分析

houhaibo 的个人博客 / 6256 / 1 / 创建于 6年前

laravel 框架采用IoC模式即（inversion of Controller）控制反转进行类的操作。将要使用的类提前绑定到容器中。今天我们讲解的不是IoC,主要通过laravel 源码分析三种绑定的区别，有利于大家对laravel框架有更进一步的了解。
一、instance 绑定

  首先我们来看一下instance方法的代码

public function instance($abstract, $instance)
{

//移除已经存在的抽象的别名
$this->removeAbstractAlias($abstract);

//检查是否已经存在该别名的绑定的对象
$isBound=$this->bound($abstract);
unset($this->aliases[$abstract]);

// We'll check to determine if this type has been bound before, and if it has
// we will fire the rebound callbacks registered with the container and it
// can be updated with consuming classes that have gotten resolved here.
$this->instances[$abstract] = $instance;

// 判断是否已经绑定
if ($isBound) {
    $this->rebound($abstract);
}

}

可以看到在instance方法中，首先移除已经存在的相同的别名，然后将对象存入$this->instance 数组中。然后完成了绑定。

二、bind 绑定

同样的，我们先贴出代码

public function bind($abstract, $concrete = null, $shared = false)
{
// If no concrete type was given, we will simply set the concrete type to the
// abstract type. After that, the concrete type to be registered as shared
// without being forced to state their classes in both of the parameters.

//移除旧的实例
$this->dropStaleInstances($abstract);
if (is_null($concrete)) {
    $concrete = $abstract;
}
// If the factory is not a Closure, it means it is just a class name which is
// bound into this container to the abstract type and we will just wrap it
// up inside its own Closure to give us more convenience when extending.
if (! $concrete instanceof Closure) {
    $concrete = $this->getClosure($abstract, $concrete);
}
// 创建一个包含变量与其值的数组。
//对每个参数，compact() 在当前的符号表中查找该变量名并将它添加到输出的数组中，变量名成为键名而变量的内容成为该键的值。简单说，它做的事和 extract() 正好相反。返回将所有变量添加进去后的数组。
$this->bindings[$abstract] = compact('concrete', 'shared');

// If the abstract type was already resolved in this container we'll fire the
// rebound listener so that any objects which have already gotten resolved
// can have their copy of the object updated via the listener callbacks.
//检查是否解析过 或则 已经存在所要绑定对象对应的实例
if ($this->resolved($abstract)) {
    $this->rebound($abstract);
}

}

使用bind 的形式如下：

$this->app->bind('HelpSpot\API', function ($app) {
return new HelpSpot\API($app->make('HttpClient'));
});

在bind 方法中首先移除旧的实例，绑定的对象实例一般是放在闭包中，如果第二个参数不是闭包，是类名，会通过getClosure函数将类名封装进闭包中，然后在闭包中通过容器的make或build函数解析该类。绑定会将相应的闭包以及是否share 放进$this->bindings数组中。在解析的时候调用。
singleton 绑定

/**

Register a shared binding in the container.
绑定到容器的对象只会被解析一次，之后的调用都返回相同的实例：
@param string|array $abstract
@param \Closure|string|null $concrete
@return void
*/
public function singleton($abstract, $concrete = null)
{
$this->bind($abstract, $concrete, true);
}

可以知道singleton 只是bind的一个调用。

这就是对laravel框架中三个绑定的源码分析。