yii2阅读随笔12

<?php

/**
     * Checks if a property value is null.
     *  检查属性值是否为空。
     * This method will check in the following order and act accordingly:
     * 此方法将在以下顺序检查并相应地采取行动：
     *  - a property defined by a setter: return whether the property value is null
     *   通过setter定义的属性：返回是否将属性值为空 
     *  - a property of a behavior: return whether the property value is null

     *  属性的行为：返回属性值是否为空 
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `isset($component->property)`.
     *
     * 重写 Object 中的 isset 方法，添加对 behaviors 的处理，循环 behaviors，如果其中有相应的属性，就认为有
     *
     * @param string $name the property name or the event name
     * @return boolean whether the named property is null
     */
    public function __isset($name)
    {
        $getter = 'get' . $name;
        if (method_exists($this, $getter)) {
            // 如果 $getter 方法存在，且不为 null，就返回 true
            return $this->$getter() !== null;
        } else {
            // behavior property
            $this->ensureBehaviors();
            // 循环所有的 behavior
            foreach ($this->_behaviors as $behavior) {
                if ($behavior->canGetProperty($name)) {
                    // 如果 behavior 中有 $name 属性，且不为 null，就返回 true
                    return $behavior->$name !== null;
                }
            }
        }
        return false;
    }
    /**
     * Sets a component property to be null.
     * 将组件属性设置为空。 
     * This method will check in the following order and act accordingly:
     * 此方法将在以下顺序检查并相应地采取行动：
     *  - a property defined by a setter: set the property value to be null
     *  通过setter定义的属性：设置该属性值为空 
     *  - a property of a behavior: set the property value to be null
     * 属性的行为：将属性值设为空 
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `unset($component->property)`.
     *
     * 重写 Object 中的 unset 方法，添加对 behaviors 的处理，循环 behaviors，如果其中有相应的属性，设置为空
     *
     * @param string $name the property name
     * @throws InvalidCallException if the property is read only.
     */
    public function __unset($name)
    {
        $setter = 'set' . $name;
        if (method_exists($this, $setter)) {
            // 如果 $setter 方法存在，且不为 null，就返回 true
            $this->$setter(null);
            return;
        } else {
            // behavior property
            $this->ensureBehaviors();
            // 循环所有的 behavior
            foreach ($this->_behaviors as $behavior) {
                if ($behavior->canSetProperty($name)) {
                    // 如果 behavior 中有 $name 属性，就将该属性设为 null
                    $behavior->$name = null;
                    return;
                }
            }
        }
        throw new InvalidCallException('Unsetting an unknown or read-only property: ' . get_class($this) . '::' . $name);
    }
    /**
     * Calls the named method which is not a class method.
     * 称为非类方法的命名方法。 
     * This method will check if any attached behavior has
     * the named method and will execute it if available.
     *
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when an unknown method is being invoked.
     *
     * 重写 Object 中的 call 方法，添加对 behaviors 的处理，循环 behaviors，如果其中有相应方法，就执行该 behavior 的方法
     *
     * @param string $name the method name
     * @param array $params method parameters
     * @return mixed the method return value
     * @throws UnknownMethodException when calling unknown method
     */
    public function __call($name, $params)
    {
        $this->ensureBehaviors();
        foreach ($this->_behaviors as $object) {
            if ($object->hasMethod($name)) {
                // behavior 中存在名为 $name 的方法，就执行它
                // call_user_func_array — 调用回调函数，并把一个数组参数作为回调函数的参数
                return call_user_func_array([$object, $name], $params);
            }
        }
        throw new UnknownMethodException('Calling unknown method: ' . get_class($this) . "::$name()");
    }
    /**
     * This method is called after the object is created by cloning an existing one.
     * It removes all behaviors because they are attached to the old object.
     *
     * 执行 clone 时，将其 _events 和 _behaviors 设置为空
     * 对象复制可以通过 clone 关键字来完成（如果可能，这将调用对象的 __clone() 方法）。对象中的 __clone() 方法不能被直接调用。
     * ~~~
     * $copy_of_object = clone $object;
     * ~~~
     * 当对象被复制后，PHP 5 会对对象的所有属性执行一个浅复制（shallow copy）。所有的引用属性 仍然会是一个指向原来的变量的引用。
     */
    public function __clone()
    {
        // 对象复制时，将它的 _events 设置为空数组，将 _behaviors 设置为 null
        $this->_events = [];
        $this->_behaviors = null;
    }