速战速决 4 - PHP: 类基础, 抽象类, 接口, trait

<span>php
</span><span>/*</span><span>*
 * 类的相关知识点 1（基础）
 *
 * 规范：命名空间与目录路径对应，类名与文件名对应，文件以 .class.php 为后缀名
 </span><span>*/</span><span>class</span><span> MyClass1
{
    </span><span>//</span><span> 类常量，没有“$”符号，不能被覆盖</span><span>const</span> MyConstant = 'constant value'<span>;
    </span><span>//</span><span> 静态属性</span><span>static</span><span>$myStaticProperty</span> = "static property"<span>;

    </span><span>//</span><span> 对于属性和方法的访问控制有 private protected public（默认值）</span><span>private</span><span>$_name</span><span>;
    </span><span>private</span><span>$_age</span><span>;

    </span><span>//</span><span> 构造函数
    // PHP 中的魔术方法（magic method）均以 __（两个下划线）开头（类似的还有 __destruct()，__call()，__callStatic()，__get()，__set()，__isset()，__unset()，__sleep()，__wakeup()，__toString()，__invoke()，__set_state() 和 __clone() 等）</span><span>function</span><span> __construct()
    {
        </span><span>echo</span> "MyClass1 construct"<span>;
        </span><span>echo</span> "<br>"<span>;

        </span><span>//</span><span> 获取参数个数</span><span>$args_num</span> = <span>func_num_args</span><span>();

        </span><span>if</span> (<span>$args_num</span> == 1<span>)
        {
            </span><span>//</span><span> $this 代表当前对象，是指向类实例的指针</span><span>$this</span>->_name = <span>func_get_arg</span>(0<span>);
        }
        </span><span>else</span><span>if</span> (<span>$args_num</span> == 2<span>)
        {
            </span><span>$this</span>->_name = <span>func_get_arg</span>(0<span>);
            </span><span>$this</span>->_age = <span>func_get_arg</span>(1<span>);
        }
        </span><span>else</span><span>        {

        }
    }

    </span><span>//</span><span> 析构函数</span><span>function</span><span> __destruct()
    {
        </span><span>print</span> "MyClass1 destruct"<span>;
        </span><span>echo</span> "<br>"<span>;
    }

    </span><span>//</span><span> 构造函数，此种方式在 PHP 5.3.3 或以上可支持
    // 此种方式的构造函数也可以当做方法被调用</span><span>public</span><span>function</span><span> MyClass1()
    {
        </span><span>echo</span> "i am not a construct, i am a method"<span>;
    }

    </span><span>//</span><span> 静态方法</span><span>public</span><span>static</span><span>function</span><span> myStaticMethod()
    {
        </span><span>return</span> "static method"<span>;
    }

    </span><span>//</span><span> 方法</span><span>public</span><span>function</span><span> getInfo()
    {
        </span><span>//</span><span> $this 代表当前对象，是指向类实例的指针</span><span>return</span> "name: " . <span>$this</span>->_name . ", age: " . <span>$this</span>-><span>_age;
    }

    </span><span>//</span><span> 不直接支持方法的重载（overload），可以通过相关的魔术方法来实现（参见：class3.php）
    // public function getInfo($name) { }

    // 带参数类型约束的方法，类型约束不能用于 int 或 string 之类的标量类型
    // 本例约束了参数 $ary 必须是 array 类型</span><span>public</span><span>function</span> getFirst(<span>array</span><span>$ary</span><span>)
    {
        </span><span>return</span><span>$ary</span>[0<span>];
    }
}

</span><span>//</span><span> 被声明为 final 的类或属性或方法，无法继承
// 只能继承一个类</span><span>final</span><span>class</span> MyClass2 <span>extends</span><span> MyClass1
{
    </span><span>//</span><span> 构造函数可以为参数设置默认值（方法或函数也可以为参数设置默认值）</span><span>function</span> __construct(<span>$name</span> = "wanglei", <span>$age</span> = 100<span>)
    {
        </span><span>echo</span> "MyClass2 construct"<span>;
        </span><span>echo</span> "<br>"<span>;

        </span><span>//</span><span> parent 代表当前类的基类</span>        parent::__construct(<span>$name</span>, <span>$age</span><span>);

        </span><span>//</span><span> self 代表当前类
        // $this 代表当前对象，是指向类实例的指针</span><span>    }

    </span><span>//</span><span> 析构函数</span><span>function</span><span> __destruct()
    {
        </span><span>print</span> "MyClass2 destruct"<span>;
        </span><span>echo</span> "<br>"<span>;

        parent</span>::<span>__destruct();
    }

    </span><span>//</span><span> 覆盖基类的同名方法（override）</span><span>public</span><span>function</span><span> getInfo()
    {
        </span><span>//</span><span> $this 代表当前对象，指向类实例的指针</span><span>return</span> "MyClass2 - " . parent::<span>getInfo();
    }
}

</span><span>//</span><span> 类的实例化</span><span>$objClass1</span> = <span>new</span> MyClass1("webabcd", 35<span>);
</span><span>//</span><span> 通过 -> 调用实例方法或实例属性</span><span>echo</span><span>$objClass1</span>-><span>getInfo();
</span><span>echo</span> "<br>"<span>;
</span><span>//</span><span> 通过 -> 调用实例方法或实例属性（MyClass1() 是构造函数，也可以当做方法被调用）</span><span>echo</span><span>$objClass1</span>-><span>MyClass1();
</span><span>echo</span> "<br>"<span>;

</span><span>$objClass2</span> = <span>new</span><span> MyClass2();
</span><span>echo</span><span>$objClass2</span>-><span>getInfo();
</span><span>echo</span> "<br>"<span>;

</span><span>//</span><span> instanceof - 用于判断一个对象是否是指定类的实例</span><span>if</span>(<span>$objClass2</span><span> instanceof MyClass1)
{
    </span><span>echo</span> '$objClass2 instanceof MyClass1'<span>;
    </span><span>echo</span> "<br>"<span>;
}

</span><span>//</span><span> 通过 :: 调用类常量或静态属性或静态方法</span><span>echo</span> MyClass1::<span>MyConstant;
</span><span>echo</span> "<br>"<span>;

</span><span>//</span><span> 通过 :: 调用类常量或静态属性或静态方法</span><span>echo</span> MyClass1::<span>$myStaticProperty</span><span>;
</span><span>echo</span> "<br>"<span>;

</span><span>//</span><span> variable class（可变类），将变量的值作为类名</span><span>$className</span> = 'MyClass1'<span>;
</span><span>//</span><span> variable method（可变方法），将变量的值作为方法名</span><span>$methodName</span> = 'myStaticMethod'<span>;
</span><span>//</span><span> 通过 :: 调用类常量或静态属性或静态方法</span><span>echo</span><span>$className</span>::<span>$methodName</span><span>();
</span><span>echo</span> "<br>"<span>;

</span><span>//</span><span> 调用带参数类型约束的方法</span><span>echo</span><span>$objClass1</span>->getFirst(<span>array</span>("a", "b", "c"<span>));
</span><span>echo</span> "<br>";

<span>php
</span><span>/*</span><span>*
 * 类的相关知识点 2（抽象类，接口，trait）
 </span><span>*/</span><span>//</span><span> 抽象类</span><span>abstract</span><span>class</span><span> MyAbstractClass
{
    </span><span>//</span><span> 抽象方法，子类必须定义这些方法</span><span>abstract</span><span>protected</span><span>function</span><span> getValue1();
    </span><span>abstract</span><span>public</span><span>function</span> getValue2(<span>$param1</span><span>);

    </span><span>//</span><span> 普通方法（非抽象方法）</span><span>public</span><span>function</span><span> getValue0()
    {
        </span><span>return</span> "getValue0"<span>;
    }
}

</span><span>//</span><span> 接口</span><span>interface</span><span> MyInterface1
{
    </span><span>//</span><span> 接口常量，不能被覆盖</span><span>const</span> MyConstant = 'constant value'<span>;
    </span><span>public</span><span>function</span><span> getValue3();
}

</span><span>//</span><span> 接口</span><span>interface</span> MyInterface2 <span>extends</span><span> MyInterface1
{
    </span><span>public</span><span>function</span><span> getValue4();
}

</span><span>//</span><span> 接口</span><span>interface</span><span> MyInterface3
{
    </span><span>public</span><span>function</span><span> getValue5();
}

</span><span>//</span><span> trait（可以 use 多个，允许有实现代码，但是本身不能实例化）</span><span>trait MyTrait1
{
    </span><span>//</span><span> 可以具有方法，静态方法，属性等</span><span>function</span><span> getValue6()
    {
        </span><span>return</span> "getValue6"<span>;
    }
}

</span><span>//</span><span> trait（可以 use 多个，允许有实现代码，但是本身不能实例化）</span><span>trait MyTrait2
{
    </span><span>//</span><span> 抽象方法（use 这个 trait 的类必须要定义这个方法）</span><span>abstract</span><span>function</span><span> getValue7();
}

</span><span>//</span><span> trait（可以 use 多个，允许有实现代码，但是本身不能实例化）</span><span>trait MyTrait3
{
    </span><span>function</span><span> getValue6()
    {
        </span><span>return</span> "getValue6"<span>;
    }

    </span><span>function</span><span> getValue8()
    {
        </span><span>return</span> "getValue8"<span>;
    }
}

</span><span>//</span><span> 必须实现所有抽象方法和接口方法
// 类只能单继承，接口可以多继承</span><span>class</span> MyClass1 <span>extends</span> MyAbstractClass <span>implements</span> MyInterface2,<span> MyInterface3
{
    </span><span>//</span><span> 可以 use 多个 trait</span><span>use</span> MyTrait1,<span> MyTrait2;
    </span><span>use</span><span> MyTrait3
    {
        </span><span>//</span><span> 多 trait 间有重名的，可以指定以哪个为准</span>        MyTrait1::<span>getValue6 insteadof MyTrait3;
        </span><span>//</span><span> 可以为 trait 的指定方法设置别名（调用的时候用方法名也行，用别名也行）</span>        MyTrait3::getValue8 <span>as</span><span> alias;
    }

    </span><span>//</span><span> 可以将 protected 升级为 public</span><span>public</span><span>function</span><span> getValue1()
    {
        </span><span>return</span> "getValue1"<span>;
    }

    </span><span>//</span><span> 可以加参数，但是加的参数必须要有默认值</span><span>public</span><span>function</span> getValue2(<span>$param1</span>, <span>$param2</span> = 'param2'<span>)
    {
        </span><span>return</span> "getValue2, {<span>$param1</span>}, {<span>$param2</span>}"<span>;
    }

    </span><span>public</span><span>function</span><span> getValue3()
    {
        </span><span>return</span> "getValue3"<span>;
    }

    </span><span>public</span><span>function</span><span> getValue4()
    {
        </span><span>return</span> "getValue4"<span>;
    }

    </span><span>public</span><span>function</span><span> getValue5()
    {
        </span><span>return</span> "getValue5"<span>;
    }

    </span><span>public</span><span>function</span><span> getValue7()
    {
        </span><span>return</span> "getValue7"<span>;
    }
}

</span><span>//</span><span> 调用接口常量</span><span>echo</span> MyInterface1::<span>MyConstant;
</span><span>echo</span> "<br>"<span>;

</span><span>$myClass1</span> = <span>new</span><span> MyClass1;
</span><span>echo</span><span>$myClass1</span>-><span>getValue0();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue1();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>->getValue2("webabcd"<span>);
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue3();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue4();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue5();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue6();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue7();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>getValue8();
</span><span>echo</span> "<br>"<span>;
</span><span>echo</span><span>$myClass1</span>-><span>alias();
</span><span>echo</span> "<br>";