摘要：說(shuō)明本文主要學(xué)習(xí)的回調(diào)類(lèi)型通常在使用函數(shù)進(jìn)行回調(diào)時(shí)，如使用進(jìn)行回調(diào)時(shí)，需要傳入回調(diào)，實(shí)際上有幾種的，在中也大量使用回調(diào)，并根據(jù)場(chǎng)景不同傳入不同的回調(diào)類(lèi)型。開(kāi)發(fā)環(huán)境是把函數(shù)名作為類(lèi)型傳進(jìn)去作為回調(diào)類(lèi)型，形式如。

說(shuō)明：本文主要學(xué)習(xí)PHP的回調(diào)類(lèi)型callback type,通常在使用函數(shù)進(jìn)行回調(diào)時(shí)，如使用call_user_func($callback, $parameters)進(jìn)行回調(diào)時(shí)，需要傳入回調(diào)callback，實(shí)際上有幾種callback type的，在Laravel中也大量使用回調(diào)，并根據(jù)場(chǎng)景不同傳入不同的回調(diào)類(lèi)型。

開(kāi)發(fā)環(huán)境：Laravel5.3 + PHP7

Function Callback Type是把函數(shù)名作為callable類(lèi)型傳進(jìn)去作為回調(diào)類(lèi)型，形式如：($function_name, $dependency)。Static Class Method Callable Type與其類(lèi)似，是把類(lèi)名+靜態(tài)方法名傳進(jìn)去作為回調(diào)類(lèi)型，形式如：("$class_name::$static_method_name", $dependency)?？聪翽HPUnit測(cè)試，看看如何使用callback type，爆綠燈：

assertSame($expected, $actual);
    }
    
    public function testStaticClassMethodCallback()
    {
        // Arrange
        $expected = "container";
        
        // Actual
        $actual = call_user_func("MyRightCapitalContainerTestsStaticClassMethodCallback::staticClassMethod", "container"); // ("$class_name::$static_method_name", $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
}

function functionCallback($app)
{
    return $app;
}

class StaticClassMethodCallback
{
    public static function staticClassMethod($app)
    {
        return $app;
    }
}

Class Method Callback Type也是類(lèi)名+靜態(tài)方法名，只不過(guò)形式稍不一樣，形式如：([$class_name, $method_name], $dependency)。Relation Class Method Callback Type是可以使用父類(lèi)的方法傳進(jìn)去作為回調(diào)，形式如：([$class_name, "parent::$method_name"], $dependency)。寫(xiě)個(gè)PHPUnit測(cè)試看下使用：

    public function testClassMethodCallback()
    {
        // Arrange
        $expected = "container";
        
        // Actual
        $actual = call_user_func([ClassMethodCallback::class, "classMethod"], "container"); // ([$class_name, $method_name], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    public function testRelationClassMethodCallback()
    {
        // Arrange
        $expected = "container/container";
        
        // Actual
        $actual = call_user_func([ClassMethodCallback::class, "parent::classMethod"], "container"); // ([$class_name, "parent::$method_name"], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    
    class ClassMethodCallback extends ParentClassMethodCallback
    {
        public static function classMethod($app)
        {
            return $app;
        }
    }
    
    class ParentClassMethodCallback
    {
        public static function classMethod($app)
        {
            return $app . "/" . $app;
        }
    }

Object Method Callback Type是把對(duì)象方法作為參數(shù)傳進(jìn)去作為回調(diào)，形式如：([$object, $method_name], $dependency)，寫(xiě)個(gè)PHPUnit測(cè)試：

    public function testObjectMethodCallback()
    {
        // Arrange
        $class_method_callback = new ClassMethodCallback();
        $expected = "container";
        
        // Actual
        $actual = call_user_func([$class_method_callback, "objectMethod"], "container"); // ([$object, $method_name], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    class ClassMethodCallback extends ParentClassMethodCallback
    {
        public static function classMethod($app)
        {
            return $app;
        }
        
        public function objectMethod($app)
        {
            return $app;
        }
    }

把Closure作為參數(shù)傳進(jìn)去作為回調(diào)參數(shù)這種方式在Laravel中大量使用，比如Laravel的Pipeline源碼就大量使用這種方式，Pipeline的源碼可看：Laravel學(xué)習(xí)筆記之Middleware源碼解析。寫(xiě)下PHPUnit測(cè)試看下：

    public function testClosureCallback()
    {
        // Arrange
        
        // Actual
        $actual       = call_user_func(getClosure(), "stack", "pipe");
        $actual_value = call_user_func($actual, "request");
        // Assert
        $this->assertInstanceOf(Closure::class, $actual);
        $this->assertSame("request/stack/pipe", $actual_value);
    }
    
    
    function getClosure()
    {
        return function ($stack, $pipe) {
            return function ($passable) use ($stack, $pipe) {
                return $passable . "/" . $stack . "/" . $pipe;
            };
        };
    }
    

最后，給出整個(gè)源碼和測(cè)試結(jié)果：

assertSame($expected, $actual);
    }
    
    public function testStaticClassMethodCallback()
    {
        // Arrange
        $expected = "container";
        
        // Actual
        $actual = call_user_func("MyRightCapitalContainerTestsStaticClassMethodCallback::staticClassMethod", "container"); // ("$class_name::$static_method_name", $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    public function testClassMethodCallback()
    {
        // Arrange
        $expected = "container";
        
        // Actual
        $actual = call_user_func([ClassMethodCallback::class, "classMethod"], "container"); // ([$class_name, $method_name], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    public function testRelationClassMethodCallback()
    {
        // Arrange
        $expected = "container/container";
        
        // Actual
        $actual = call_user_func([ClassMethodCallback::class, "parent::classMethod"], "container"); // ([$class_name, "parent::$method_name"], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    public function testObjectMethodCallback()
    {
        // Arrange
        $class_method_callback = new ClassMethodCallback();
        $expected              = "container";
        
        // Actual
        $actual = call_user_func([$class_method_callback, "objectMethod"], "container"); // ([$object, $method_name], $dependency)
        
        // Assert
        $this->assertSame($expected, $actual);
    }
    
    public function testClosureCallback()
    {
        // Arrange
        
        // Actual
        $actual       = call_user_func(getClosure(), "stack", "pipe");
        $actual_value = call_user_func($actual, "request");
        // Assert
        $this->assertInstanceOf(Closure::class, $actual);
        $this->assertSame("request/stack/pipe", $actual_value);
    }
}

function getClosure()
{
    return function ($stack, $pipe) {
        return function ($passable) use ($stack, $pipe) {
            return $passable . "/" . $stack . "/" . $pipe;
        };
    };
}

function functionCallback($app)
{
    return $app;
}

class StaticClassMethodCallback
{
    public static function staticClassMethod($app)
    {
        return $app;
    }
}

class ClassMethodCallback extends ParentClassMethodCallback
{
    public static function classMethod($app)
    {
        return $app;
    }
    
    public function objectMethod($app)
    {
        return $app;
    }
}

class ParentClassMethodCallback
{
    public static function classMethod($app)
    {
        return $app . "/" . $app;
    }
}

總結(jié)：本文主要總結(jié)下PHP的Callback Type，便于提高自己的代碼設(shè)計(jì)能力。遇到好的技術(shù)再聊，到時(shí)見(jiàn)。

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