前言

公司的后臺(tái)是使用Laravel框架寫的，最近在把其中的訂單處理部分抽出來，準(zhǔn)備寫個(gè)單獨(dú)的Library。特地好好的研究了一下設(shè)計(jì)模式诸迟，Laravel學(xué)院上面有一個(gè)專題，便是談設(shè)計(jì)模式的愕乎，甚好！

背景知識(shí)

• php/composer
• IoC

安裝

直接使用composer：

composer require illuminate/container

Laravel之外使用Illuminate/Container

還是以我的Order項(xiàng)目為例比肄，用其中的部分作為講解。先看一下部分架構(gòu)圖囊陡。

架構(gòu)圖

• Container

首先需要在自己項(xiàng)目中定義一個(gè)容器對(duì)象，來“容納”所有的實(shí)例或者方法等遏片。這里我將Cashier類作為統(tǒng)一的對(duì)外處理對(duì)象嘹害，它繼承自Illuminate\Container\Container撮竿。

一般配置信息會(huì)作為容器的構(gòu)造函數(shù)的參數(shù)。在Laravel中笔呀，由于配置內(nèi)容較多幢踏，這一形式表現(xiàn)為__construct函數(shù)中的$basePath參數(shù)。通過約定的目錄結(jié)構(gòu)結(jié)合$appPath動(dòng)態(tài)讀取配置信息许师。本項(xiàng)目則選擇直接給予一個(gè)Config類的形式房蝉，注入配置信息。Config類實(shí)質(zhì)是一個(gè)鍵值對(duì)的數(shù)組微渠。

class Cashier extends Container implements \WilliamWei\FancyOrder\Contracts\Cashier
{
    protected $providers = [
        OrderServiceProvider::class,
        PipelineServiceProvider::class,
    ];


    public function __construct($config)
    {
        $this['config'] = function () use ($config) {
            return new Config($config);
        };

        //register the provider
        foreach ($this->providers as $provider)
        {
            $provider = new $provider();
            $provider->register($this);
        }

    }
}

Illuminate\Container\Container已經(jīng)實(shí)現(xiàn)了ArrayAccess接口搭幻，可以直接以數(shù)組方式訪問容器中的對(duì)象。構(gòu)造時(shí)敛助，首先為config對(duì)象定義實(shí)例化的閉包函數(shù)粗卜。然后依次將各個(gè)模塊對(duì)應(yīng)的ServiceProvider進(jìn)行注冊(cè)。

• ServiceProvider

將項(xiàng)目劃分為更小的子模塊有助于控制規(guī)模纳击，可以大大提高可維護(hù)性以及可測(cè)試性续扔。每個(gè)子模塊都有一個(gè)ServiceProvider，用于暴露本模塊可提供的服務(wù)對(duì)象焕数。自定義的ServiceProvider可以繼承Illuminate\Support\ServiceProvider纱昧，這里我是選擇自己實(shí)現(xiàn)的ServiceProvider。
接口：

interface ServiceProvider
{
    public function register(Container $app);
}

以PipelineServiceProvider為例:

class PipelineServiceProvider implements ServiceProvider
{
    public function register(Container $app)
    {
        $workers = [];

        foreach ($app['config']['pipeline_workers'] as $name => $worker)
        {
            $app->bind($name,function($app) use ($worker) {
                return new $worker();
            });

            array_push($workers,$app[$name]);
        }

        $app->bind('pipeline',function($app) use ($workers) {
            return new Pipeline($workers);
        });
    }
}

PipelineServiceProvider在register方法中堡赔，將特定函數(shù)與實(shí)例的名字進(jìn)行綁定识脆，當(dāng)通過該名字訪問實(shí)例時(shí)，若對(duì)象不存在善已，則容器會(huì)調(diào)用被綁定的函數(shù)來實(shí)例化一個(gè)對(duì)象灼捂，并將其置于容器，以供后續(xù)調(diào)用使用换团。對(duì)于Pipeline悉稠，他并不需要關(guān)心是哪些Pipeworker在工作，只需要知道他們存在艘包，并且可以正常工作就好的猛，從而以這種形式達(dá)到解耦目的。

當(dāng)然有可能有時(shí)候需要訪問容器內(nèi)其他對(duì)象想虎，則可以將容器本身作為構(gòu)造函數(shù)的參數(shù)傳入卦尊，如：

$app->bind('pipeline',function($app) use ($workers) {
    return new Pipeline($app,$workers);
});

那么在Pipeline內(nèi)部就可以通過
$this->app['XXX']的形式訪問XXX對(duì)象，同時(shí)也無需關(guān)心XXX是如何構(gòu)造的舌厨。

代碼分析

這里的代碼分析部分只關(guān)注主體部分岂却，不會(huì)面面具到的分析到每個(gè)函數(shù)。

可以看到整個(gè)包一共就3個(gè)PHP文件，最核心的是Container.php淌友，它定義了容器類煌恢，并實(shí)現(xiàn)了其中絕大多數(shù)功能。當(dāng)我們bind一個(gè)實(shí)例到通過[]下標(biāo)訪問時(shí)發(fā)生了什么震庭？

    /**
     * Register a binding with the container.
     *
     * @param  string|array  $abstract
     * @param  \Closure|string|null  $concrete
     * @param  bool  $shared
     * @return void
     */
    public function bind($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.
        $this->dropStaleInstances($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);
        }

        $this->bindings[$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.
        if ($this->resolved($abstract)) {
            $this->rebound($abstract);
        }
    }

這是bind函數(shù)瑰抵，當(dāng)我們執(zhí)行一個(gè)綁定操作時(shí)，容器首先會(huì)把該名字之前綁定的實(shí)例與別名清除掉器联，即$this->dropStaleInstances($abstract);如果該名字對(duì)應(yīng)實(shí)例是已經(jīng)解析過的二汛，則會(huì)觸發(fā)rebound,執(zhí)行對(duì)應(yīng)回調(diào)。對(duì)于第一次綁定則不會(huì)出現(xiàn)這種情況拨拓。到此bind就結(jié)束了肴颊。

當(dāng)通過下標(biāo)方式獲取實(shí)例時(shí)

    public function offsetGet($key)
    {
        return $this->make($key);
    }

可以看到調(diào)用了make方法。

    /**
     * Resolve the given type from the container.
     *
     * @param  string  $abstract
     * @return mixed
     */
    public function make($abstract)
    {
        $needsContextualBuild = ! is_null(
            $this->getContextualConcrete($abstract = $this->getAlias($abstract))
        );

        // If an instance of the type is currently being managed as a singleton we'll
        // just return an existing instance instead of instantiating new instances
        // so the developer can keep using the same objects instance every time.
        if (isset($this->instances[$abstract]) && ! $needsContextualBuild) {
            return $this->instances[$abstract];
        }

        $concrete = $this->getConcrete($abstract);

        // We're ready to instantiate an instance of the concrete type registered for
        // the binding. This will instantiate the types, as well as resolve any of
        // its "nested" dependencies recursively until all have gotten resolved.
        if ($this->isBuildable($concrete, $abstract)) {
            $object = $this->build($concrete);
        } else {
            $object = $this->make($concrete);
        }

        // If we defined any extenders for this type, we'll need to spin through them
        // and apply them to the object being built. This allows for the extension
        // of services, such as changing configuration or decorating the object.
        foreach ($this->getExtenders($abstract) as $extender) {
            $object = $extender($object, $this);
        }

        // If the requested type is registered as a singleton we'll want to cache off
        // the instances in "memory" so we can return it later without creating an
        // entirely new instance of an object on each subsequent request for it.
        if ($this->isShared($abstract) && ! $needsContextualBuild) {
            $this->instances[$abstract] = $object;
        }

        $this->fireResolvingCallbacks($abstract, $object);

        $this->resolved[$abstract] = true;

        return $object;
    }

略有些復(fù)雜渣磷，大致流程是先檢查實(shí)例數(shù)組中該實(shí)例是否存在婿着，存在的話則返回。對(duì)于不存在的情況醋界，由于我們是實(shí)用閉包的方式進(jìn)行bind竟宋，所以會(huì)調(diào)用該閉包，即$object = $this->build($concrete);得到$object形纺。后面會(huì)通知該實(shí)例對(duì)應(yīng)類的子類丘侠，告知他們?cè)搶?shí)例已被創(chuàng)建。注冊(cè)該實(shí)例到實(shí)例數(shù)組逐样，（如果存在解析完成回調(diào)函數(shù)則會(huì)去執(zhí)行）蜗字，返回實(shí)例。

這個(gè)便是容器內(nèi)部的一個(gè)流程脂新。

BoundMethod.php主要以靜態(tài)的形式實(shí)現(xiàn)了直接調(diào)用某個(gè)類的某一方法的目標(biāo)挪捕。

ContextualBindingBuilder.php則主要是用于將實(shí)例與一個(gè)上下文情景進(jìn)行綁定。這兩部分都是比較高級(jí)的內(nèi)容争便，這里不作展開了担神。

歡迎關(guān)注個(gè)人博客 :)