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Laravel学习笔记之PHP反射(Reflection) (上)

JessYanCoding / 1463人阅读

摘要:说明中经常使用的反射特性来设计代码,本文主要学习的反射特性,来提高写代码时的设计质量。提供一套检测的两个工具包和,类似于探针一样的东西来探测这些一等公民。限于篇幅,下篇再聊下反射。

说明:Laravel中经常使用PHP的反射特性来设计代码,本文主要学习PHP的反射特性,来提高写代码时的设计质量。PHP提供一套检测class, interface, trait, property, method的两个工具包:Introspection FunctionsReflection API,类似于探针一样的东西来探测这些一等公民。本文先看下Introspection Functions的使用。

开发环境: Laravel5.3 + PHP7

Introspection Functions

Introspection Functions是用来操作object class的一些函数,PHP提供了大量的Introspection Functions来操作class, interface, trait, method, property:

class_exists()

interface_exists()

method_exists()

property_exists()

trait_exists()

class_alias()

get_class()

get_parent_class()

get_called_class()

get_class_methods()

get_class_vars()

get_object_vars()

is_subclass_of()

is_a()

class_exists()

Laravel源码中好多个地方使用到class_exists()方法来判断指定类是否存在,如IlluminateDatabaseConnection::isDoctrineAvailable()的源码:

    public function isDoctrineAvailable()
    {
        return class_exists("DoctrineDBALConnection"); // DoctrineDBALConnection::class类是否存在,大小写不敏感
    }

写个PHPUnit测试下(爆绿灯,说明是正确的,这里不截图了。后面所有Introspection的测试都放在IntrospectionTest这个单元测试里):

namespace MyRightCapitalContainerTests;

class IntrospectionTest extends PHPUnit_Framework_TestCase
{
    public function testClassExists()
    {
        // Arrange
        
        // Actual
        $class_exists = class_exists(TestClassExists::class);
        // Assert
        $this->assertTrue($class_exists);
    }
}

class TestClassExists
{
    
}
interface_exists()

interface_exists()是用来检查接口是否存在,写个PHPUnit测试下,爆绿灯:

namespace MyRightCapitalContainerTests;

class IntrospectionTest extends PHPUnit_Framework_TestCase
{
    public function testInterfaceExists()
    {
        // Arrange
        
        // Actual
        $interface_exists = interface_exists(TestInterfaceExists::class);
        // Assert
        $this->assertTrue($interface_exists);
    }
}

interface TestInterfaceExists
{
    
}
method_exists()

检查类的方法(private,protected,public)是否存在于指定的类对象或类名中,Laravel中很多处用到了这个函数,如Application中的register()检查service provider中register是否存在,和bootProvider()中检查service provider中boot()方法是否存在:

public function register($provider, $options = [], $force = false)
{
    ...
    
    if (method_exists($provider, "register")) {
            $provider->register();
    }
    
    ...
}
protected function bootProvider(ServiceProvider $provider)
{
    if (method_exists($provider, "boot")) {
        return $this->call([$provider, "boot"]);
    }
}

这里写个PHPUnit测试下,爆绿灯:

    public function testMethodExists()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $object_method_exists1    = method_exists($test_class_exists, "testPrivateMethodExists");
        $object_method_exists2    = method_exists($test_class_exists, "testProtectedMethodExists");
        $object_method_exists3    = method_exists($test_class_exists, "testPublicMethodExists");
        $classname_method_exists1 = method_exists(TestClassExists::class, "testPrivateMethodExists");
        $classname_method_exists2 = method_exists(TestClassExists::class, "testProtectedMethodExists");
        $classname_method_exists3 = method_exists(TestClassExists::class, "testPublicMethodExists");
        
        // Assert
        $this->assertTrue($object_method_exists1);
        $this->assertTrue($object_method_exists2);
        $this->assertTrue($object_method_exists3);
        $this->assertTrue($classname_method_exists1);
        $this->assertTrue($classname_method_exists2);
        $this->assertTrue($classname_method_exists3);
    }
    
    
    class TestClassExists
    {
        private function testPrivateMethodExists()
        {
        }
        
        protected function testProtectedMethodExists()
        {
        }
        
        public function testPublicMethodExists()
        {
        }
    }
property_exists()

检查该属性(private, protected, public)是否存在于类对象或类名中,Laravel很多地方用到了该函数,如IlluminateFoundationAuthRedirectsUsers::redirectPath()源码:

    public function redirectPath()
    {
        return property_exists($this, "redirectTo") ? $this->redirectTo : "/home";
    }

写个PHPUnit测试下该函数,爆绿灯:

    // class IntrospectionTest
    public function testPropertyExists()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $private_property1   = property_exists($test_class_exists, "testPrivatePropertyExists");
        $private_property2   = property_exists(TestClassExists::class, "testPrivatePropertyExists");
        $protected_property1 = property_exists($test_class_exists, "testProtectedPropertyExists");
        $protected_property2 = property_exists(TestClassExists::class, "testProtectedPropertyExists");
        $public_property1    = property_exists($test_class_exists, "testPublicPropertyExists");
        $public_property2    = property_exists(TestClassExists::class, "testPublicPropertyExists");
        
        // Assert
        $this->assertTrue($private_property1);
        $this->assertTrue($private_property2);
        $this->assertTrue($protected_property1);
        $this->assertTrue($protected_property2);
        $this->assertTrue($public_property1);
        $this->assertTrue($public_property2);
    }
    
    
    class TestClassExists
    {
        private   $testPrivatePropertyExists;
        protected $testProtectedPropertyExists;
        public    $testPublicPropertyExists;
    }
trait_exists()

检查trait是否存在,写下PHPUnit测试,爆绿灯:

    // class IntrospectionTest
    public function testTraitExists()
    {
        // Arrange
        
        // Actual
        $test_trait_exists = trait_exists(TestTraitExists::class);
        
        // Assert
        $this->assertTrue($test_trait_exists);
    }
    
    trait TestTraitExists
    {
    
    }
class_alias()

给指定类取别名,Laravel中只有一处使用了class_alias(),用来给config/app.php中$aliases[ ]注册别名,可看下Laravel学习笔记之bootstrap源码解析,看下Laravel中如何使用的:

    public function load($alias)
    {
        if (isset($this->aliases[$alias])) {
            return class_alias($this->aliases[$alias], $alias);
        }
    }

写个PHPUnit测试,爆绿灯:

    public function testClassAlias()
    {
        // Arrange
        class_alias(TestClassExists::class, "MyRightCapitalContainerTestsAliasTestClassExists");
        $test_class_exists = new TestClassExists();
        
        // Actual
        $actual = new AliasTestClassExists();
        
        //Assert
        $this->assertInstanceOf(TestClassExists::class, $actual);
        $this->assertInstanceOf(AliasTestClassExists::class, $test_class_exists);
    }
get_class()

get_class()获取对象的类名,这个函数在Laravel中大量地方在用了,如Application::getProvider($provider)方法,是个很好用的方法:

    public function getProvider($provider)
    {
        $name = is_string($provider) ? $provider : get_class($provider);

        return Arr::first($this->serviceProviders, function ($value) use ($name) {
            return $value instanceof $name;
        });
    }

写个PHPUnit测试,爆绿灯:

    public function testGetClass()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $class_name = get_class($test_class_exists);
        
        // Assert
        $this->assertSame(TestClassExists::class, $class_name);
    }
get_parent_class()

get_parent_class()是用来获取类的父类名,目前Laravel中还没用到这个函数,传入的可以是子类对象或者子类名,写个PHPUnit测试下:

    // namespace MyRightCapitalContainerTests;
    // class IntrospectionTest extends PHPUnit_Framework_TestCase
    public function testGetParentClass()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $parent_class1 = get_parent_class($child_class);
        $parent_class2 = get_parent_class(ChildClass::class);
        
        // Assert
        $this->assertSame(ParentClass::class, $parent_class1);
        $this->assertSame(ParentClass::class, $parent_class2);
    }
    
    class ChildClass extends ParentClass 
    {
        
    }
    
    class ParentClass
    {
        
    }
get_called_class()

get_called_class()获取后期静态绑定类即实际调用类的名称,Laravel中还没使用到该函数,不妨写个测试看下如何使用:

    // namespace MyRightCapitalContainerTests;
    // class IntrospectionTest extends PHPUnit_Framework_TestCase
    public function testGetCalledClass()
    {
        // Arrange
        $child_class  = new ChildClass();
        $parent_class = new ParentClass();
        
        // Actual
        $child_called_class = $child_class->testGetCalledClass();
        $parent_called_class = $parent_class->testGetCalledClass();
        
        // Assert
        $this->assertSame(ChildClass::class, $child_called_class);
        $this->assertSame(ParentClass::class, $parent_called_class);
    }
    
    class ChildClass extends ParentClass
    {
        
    }
    
    class ParentClass
    {
        public function testGetCalledClass()
        {
            return get_called_class();
        }
    }
get_class_methods()

get_class_methods()用来获取类的方法名组成一个数组(测试只能是public),Laravel只有一处用到了该方法IlluminateDatabaseEloquentModel::cacheMutatedAttributes() :line 3397,这里写个PHPUnit测试,爆绿灯:

    public function testGetClassMethod()
    {
        // Arrange
        $get_class_methods1 = get_class_methods(ChildClass::class);
        $get_class_methods2 = get_class_methods(new ChildClass());
        
        // Actual
        
        // Assert
        $this->assertFalse(in_array("testPrivateGetClassMethod", $get_class_methods1, true));
        $this->assertFalse(in_array("testPrivateGetClassMethod", $get_class_methods2, true));
        $this->assertFalse(in_array("testProtectedGetClassMethod", $get_class_methods1, true));
        $this->assertFalse(in_array("testProtectedGetClassMethod", $get_class_methods2, true));
        $this->assertTrue(in_array("testPublicGetClassMethod", $get_class_methods1, true));
        $this->assertTrue(in_array("testPublicGetClassMethod", $get_class_methods2, true));
        $this->assertTrue(in_array("testGetCalledClass", $get_class_methods1, true));
        $this->assertTrue(in_array("testGetCalledClass", $get_class_methods2, true));
    }
    
    class ChildClass extends ParentClass
    {
        private function testPrivateGetClassMethod()
        {
        }
        
        protected function testProtectedGetClassMethod()
        {
        }
        
        public function testPublicGetClassMethod()
        {
        }
    }
get_class_vars()

get_class_vars()只会读取类的public属性组成一个数组,类似于get_class_methods(),若属性没有默认值就为null,目前Laravel中还未使用,看下PHPUnit测试:

    public function testGetClassVars()
    {
        // Arrange
        
        // Actual
        $class_vars = get_class_vars(ChildClass::class);
        
        // Assert
        $this->assertArrayNotHasKey("privateNoDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("privateDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("protectedNoDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("protectedDefaultVar", $class_vars);
        $this->assertEmpty($class_vars["publicNoDefaultVar"]);
        $this->assertEquals("public_laravel", $class_vars["publicDefaultVar"]);
    }
    
    class ChildClass extends ParentClass
    {
        private   $privateNoDefaultVar;
        private   $privateDefaultVar   = "private_laravel";
        protected $protectedNoDefaultVar;
        protected $protectedDefaultVar = "protected_laravel";
        public    $publicNoDefaultVar;
        public    $publicDefaultVar    = "public_laravel";
   }     
get_object_vars()

get_object_vars()只会读取对象的public属性组成一个数组,类似于get_class_vars(), get_class_methods(),且属性没有默认值就是null,Laravel中只有一处使用到IlluminateMailJobsHandleQueuedMessage::__sleep() :line 78,写个PHPUnit测试下,爆绿灯:

    public function testGetObjectVars()
    {
        // Arrange
        $get_object_vars = new TestGetObjectVars(1, 2, 3);
        
        // Actual
        $object_vars = get_object_vars($get_object_vars);
        
        // Assert
        $this->assertArrayNotHasKey("x", $object_vars);
        $this->assertArrayNotHasKey("y", $object_vars);
        $this->assertEquals(3, $object_vars["z"]);
        $this->assertArrayNotHasKey("dot1", $object_vars);
        $this->assertArrayNotHasKey("dot2", $object_vars);
        $this->assertArrayNotHasKey("circle1", $object_vars);
        $this->assertArrayNotHasKey("circle2", $object_vars);
        $this->assertEquals(10, $object_vars["line1"]);
        $this->assertEmpty($object_vars["line2"]);
    }
    
    class TestGetObjectVars
    {
        private   $x;
        protected $y;
        public    $z;
        private   $dot1    = 10;
        private   $dot2;
        protected $circle1 = 20;
        protected $circle2;
        public    $line1   = 10;
        public    $line2;
        
        public function __construct($x, $y, $z)
        {
            
            $this->x = $x;
            $this->y = $y;
            $this->z = $z;
        }
    }
is_subclass_of()

is_subclass_of()用来判断给定类对象是否是另一给定类名的子类,Laravel中有用到,这里写下PHPUnit测试,爆绿灯:

    public function testIsSubclassOf()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $is_subclass = is_subclass_of($child_class, ParentClass::class);
        
        // Assert
        $this->assertTrue($is_subclass);
    }
is_a()

is_a()用来判定给定类对象是否是另一给定类名的对象或是子类,和is_subclass_of()有点类似,只是is_a()还可以判定是不是该类的对象,is_a()类似于instanceof操作符,Laravel中还没用到这个方法,这里写个PHPUnit测试,爆绿灯:

    public function testIsA()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $is_object   = is_a($child_class, ChildClass::class);
        $is_subclass = is_a($child_class, ParentClass::class);
        
        // Assert
        $this->assertTrue($is_object);
        $this->assertTrue($is_subclass);
    }

最后,给下整个PHPUnit的测试代码:

assertTrue($class_exists);
    }
    
    public function testInterfaceExists()
    {
        // Arrange
        
        // Actual
        $interface_exists = interface_exists(TestInterfaceExists::class);
        // Assert
        $this->assertTrue($interface_exists);
    }
    
    public function testMethodExists()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $object_method_exists1    = method_exists($test_class_exists, "testPrivateMethodExists");
        $object_method_exists2    = method_exists($test_class_exists, "testProtectedMethodExists");
        $object_method_exists3    = method_exists($test_class_exists, "testPublicMethodExists");
        $classname_method_exists1 = method_exists(TestClassExists::class, "testPrivateMethodExists");
        $classname_method_exists2 = method_exists(TestClassExists::class, "testProtectedMethodExists");
        $classname_method_exists3 = method_exists(TestClassExists::class, "testPublicMethodExists");
        
        // Assert
        $this->assertTrue($object_method_exists1);
        $this->assertTrue($object_method_exists2);
        $this->assertTrue($object_method_exists3);
        $this->assertTrue($classname_method_exists1);
        $this->assertTrue($classname_method_exists2);
        $this->assertTrue($classname_method_exists3);
    }
    
    public function testPropertyExists()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $private_property1   = property_exists($test_class_exists, "testPrivatePropertyExists");
        $private_property2   = property_exists(TestClassExists::class, "testPrivatePropertyExists");
        $protected_property1 = property_exists($test_class_exists, "testProtectedPropertyExists");
        $protected_property2 = property_exists(TestClassExists::class, "testProtectedPropertyExists");
        $public_property1    = property_exists($test_class_exists, "testPublicPropertyExists");
        $public_property2    = property_exists(TestClassExists::class, "testPublicPropertyExists");
        
        // Assert
        $this->assertTrue($private_property1);
        $this->assertTrue($private_property2);
        $this->assertTrue($protected_property1);
        $this->assertTrue($protected_property2);
        $this->assertTrue($public_property1);
        $this->assertTrue($public_property2);
    }
    
    public function testTraitExists()
    {
        // Arrange
        
        // Actual
        $test_trait_exists = trait_exists(TestTraitExists::class);
        
        // Assert
        $this->assertTrue($test_trait_exists);
    }
    
    public function testClassAlias()
    {
        // Arrange
        class_alias(TestClassExists::class, "MyRightCapitalContainerTestsAliasTestClassExists");
        $test_class_exists = new TestClassExists();
        
        // Actual
        $actual = new AliasTestClassExists();
        
        //Assert
        $this->assertInstanceOf(TestClassExists::class, $actual);
        $this->assertInstanceOf(AliasTestClassExists::class, $test_class_exists);
    }
    
    public function testGetClass()
    {
        // Arrange
        $test_class_exists = new TestClassExists();
        
        // Actual
        $class_name = get_class($test_class_exists);
        
        // Assert
        $this->assertSame(TestClassExists::class, $class_name);
    }
    
    public function testGetParentClass()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $parent_class1 = get_parent_class($child_class);
        $parent_class2 = get_parent_class(ChildClass::class);
        
        // Assert
        $this->assertSame(ParentClass::class, $parent_class1);
        $this->assertSame(ParentClass::class, $parent_class2);
    }
    
    public function testGetCalledClass()
    {
        // Arrange
        $child_class  = new ChildClass();
        $parent_class = new ParentClass();
        
        // Actual
        $child_called_class  = $child_class->testGetCalledClass();
        $parent_called_class = $parent_class->testGetCalledClass();
        
        // Assert
        $this->assertSame(ChildClass::class, $child_called_class);
        $this->assertSame(ParentClass::class, $parent_called_class);
    }
    
    public function testInArray()
    {
        $this->assertTrue(in_array("a", ["a", "b", 1], true));
    }
    
    public function testGetClassMethod()
    {
        // Arrange
        $get_class_methods1 = get_class_methods(ChildClass::class);
        $get_class_methods2 = get_class_methods(new ChildClass());
        
        // Actual
        
        // Assert
        $this->assertFalse(in_array("testPrivateGetClassMethod", $get_class_methods1, true));
        $this->assertFalse(in_array("testPrivateGetClassMethod", $get_class_methods2, true));
        $this->assertFalse(in_array("testProtectedGetClassMethod", $get_class_methods1, true));
        $this->assertFalse(in_array("testProtectedGetClassMethod", $get_class_methods2, true));
        $this->assertTrue(in_array("testPublicGetClassMethod", $get_class_methods1, true));
        $this->assertTrue(in_array("testPublicGetClassMethod", $get_class_methods2, true));
        $this->assertTrue(in_array("testGetCalledClass", $get_class_methods1, true));
        $this->assertTrue(in_array("testGetCalledClass", $get_class_methods2, true));
    }
    
    public function testGetClassVars()
    {
        // Arrange
        
        // Actual
        $class_vars = get_class_vars(ChildClass::class);
        
        // Assert
        $this->assertArrayNotHasKey("privateNoDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("privateDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("protectedNoDefaultVar", $class_vars);
        $this->assertArrayNotHasKey("protectedDefaultVar", $class_vars);
        $this->assertEmpty($class_vars["publicNoDefaultVar"]);
        $this->assertEquals("public_laravel", $class_vars["publicDefaultVar"]);
    }
    
    public function testGetObjectVars()
    {
        // Arrange
        $get_object_vars = new TestGetObjectVars(1, 2, 3);
        
        // Actual
        $object_vars = get_object_vars($get_object_vars);
        
        // Assert
        $this->assertArrayNotHasKey("x", $object_vars);
        $this->assertArrayNotHasKey("y", $object_vars);
        $this->assertEquals(3, $object_vars["z"]);
        $this->assertArrayNotHasKey("dot1", $object_vars);
        $this->assertArrayNotHasKey("dot2", $object_vars);
        $this->assertArrayNotHasKey("circle1", $object_vars);
        $this->assertArrayNotHasKey("circle2", $object_vars);
        $this->assertEquals(10, $object_vars["line1"]);
        $this->assertEmpty($object_vars["line2"]);
    }
    
    public function testIsSubclassOf()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $is_subclass = is_subclass_of($child_class, ParentClass::class);
        
        // Assert
        $this->assertTrue($is_subclass);
    }
    
    public function testIsA()
    {
        // Arrange
        $child_class = new ChildClass();
        
        // Actual
        $is_object = is_a($child_class, ChildClass::class);
        $is_subclass = is_a($child_class, ParentClass::class);
        
        // Assert
        $this->assertTrue($is_object);
        $this->assertTrue($is_subclass);
    }
}

class TestGetObjectVars
{
    private   $x;
    protected $y;
    public    $z;
    private   $dot1    = 10;
    private   $dot2;
    protected $circle1 = 20;
    protected $circle2;
    public    $line1   = 10;
    public    $line2;
    
    public function __construct($x, $y, $z)
    {
        
        $this->x = $x;
        $this->y = $y;
        $this->z = $z;
    }
}

class ChildClass extends ParentClass
{
    private   $privateNoDefaultVar;
    private   $privateDefaultVar   = "private_laravel";
    protected $protectedNoDefaultVar;
    protected $protectedDefaultVar = "protected_laravel";
    public    $publicNoDefaultVar;
    public    $publicDefaultVar    = "public_laravel";
    
    private function testPrivateGetClassMethod()
    {
    }
    
    protected function testProtectedGetClassMethod()
    {
    }
    
    public function testPublicGetClassMethod()
    {
    }
}

class ParentClass
{
    public function testGetCalledClass()
    {
        return get_called_class();
    }
}

class TestClassExists
{
    private   $testPrivatePropertyExists;
    protected $testProtectedPropertyExists;
    public    $testPublicPropertyExists;
    
    private function testPrivateMethodExists()
    {
    }
    
    protected function testProtectedMethodExists()
    {
    }
    
    public function testPublicMethodExists()
    {
    }
}

interface TestInterfaceExists
{
    
}

trait TestTraitExists
{
    
}

PHP不仅提供了检测class, interface, trait, property, method这些函数Introspection Functions,还提供了一整套的API即反射来检测class, interface, trait, property, method,这些API是好几个类组成的,提供了很多好用的方法。限于篇幅,下篇再聊下反射API。

总结:本文主要聊了下PHP提供的一套检测class, interface, trait, property, method的两个工具包:Introspection Functions和Reflection API,这里先聊到Introspection Functions。下篇再聊下Reflection API的使用,到时见。

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