yii2框架随笔17

阅读object.php

<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */
namespace yii\base;
use Yii;
/**
 * Object is the base class that implements the *property* feature.
 * Object 是一个基础类，实现了属性的功能
 *
 * A property is defined by a getter method (e.g. `getLabel`), and/or a setter method (e.g. `setLabel`). For example,
 * the following getter and setter methods define a property named `label`:
 * 一个定义了 getter 方法和/或者 setter 方法的属性
 *
 * ~~~
 * private $_label;
 *
 * public function getLabel()
 * {
 *     return $this->_label;通过getter方法取得_label的值
 * }
 *
 * public function setLabel($value)
 * {
 *     $this->_label = $value;通过setter方法设置_label的值
 * }
 * ~~~
 *
 * Property names are *case-insensitive*.
 * 属性名是大小写敏感的
 *
 * A property can be accessed like a member variable of an object. Reading or writing a property will cause the invocation
 * of the corresponding getter or setter method. For example,
 * 属性能够像一个成员变量一样被访问，读、写将会调用对应的getter或者setter方法
 *
 * ~~~
 * // equivalent to $label = $object->getLabel();
 * $label = $object->label;
 * // equivalent to $object->setLabel('abc');
 * $object->label = 'abc';
 * ~~~
 *
 * If a property has only a getter method and has no setter method, it is considered as *read-only*. In this case, trying
 * to modify the property value will cause an exception.
 * 如果一个属性只有getter方法，那么这个属性是只读的，如果这样，试图修改这个属性的值，将会抛出异常.
 * One can call [[hasProperty()]], [[canGetProperty()]] and/or [[canSetProperty()]] to check the existence of a property.
 * 可以调用 [[hasProperty()]], [[canGetProperty()]] and/or [[canSetProperty()]] 检查一个属性是否存在。
 * Besides the property feature, Object also introduces an important object initialization life cycle. In particular,
 * creating an new instance of Object or its derived class will involve the following life cycles sequentially:
 * 除了属性特征，还引入了一个重要的对象初始化。特别的，创建一个新实例的对象或其派生类将涉及以下顺序生命周期:
 * 1. the class constructor is invoked;
 * 调用类的构造函数;
 * 2. object properties are initialized according to the given configuration;
 * 根据给定的对象属性初始化配置;
 * 3. the `init()` method is invoked.
 * init()的调用方法。
 *
 * In order to ensure the above life cycles, if a child class of Object needs to override the constructor,
 * it should be done like the following:
 * 为了确保上述的运转，如果一个子类的对象需要覆盖构造函数,它应该如下：
 * ~~~
 * public function __construct($param1, $param2, ..., $config = [])
 * {
 *     ...
 *     parent::__construct($config); //构造函数。
 * }
 * ~~~
 *
 * That is, a `$config` parameter (defaults to `[]`) should be declared as the last parameter
 * of the constructor, and the parent implementation should be called at the end of the constructor.
 *
 * Yii最基础的类，大多数类都继承了该类
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class Object implements Configurable
{
    /**
     * Returns the fully qualified name of this class.
     * 获取静态方法调用的类名。返回类的名称，如果不是在类中调用则返回 FALSE。
     *
     * @return string the fully qualified name of this class.
     */
    public static function className()
    {
        // get_called_class -- 后期静态绑定（"Late Static Binding"）类的名称
        // 就是用那个类调用的这个方法，就返回那个类，返回值中带有 namespace
        return get_called_class();
    }
    /**
     * Constructor.
     * The default implementation does two things:
     * 默认实现做两件事:
     * - Initializes the object with the given configuration `$config`.
     * - Call [[init()]].
     * 构造方法实现了接口Configurable，通过传入的配置初始化对象，调用init（）方法
     * If this method is overridden in a child class, it is recommended that
     *
     * - the last parameter of the constructor is a configuration array, like `$config` here.
     *
     * - call the parent implementation at the end of the constructor.
     * 如果构造函数在子类中重写，必须调用父类的方法，且最后一个参数为配置数组
     * @param array $config name-value pairs that will be used to initialize the object properties
     */
    public function __construct($config = [])
    {
        // 根据 $config 内容初始化该对象
        if (!empty($config)) {
            Yii::configure($this, $config);
        }
        // 调用 init() 方法，继承该类的类可以重写 init 方法，用于初始化
        $this->init();
    }
    /**
     * Initializes the object.
     * 初始化对象
     * This method is invoked at the end of the constructor after the object is initialized with the
     * given configuration.
     * 在构造函数的末尾调用，可以重写 init 方法，用于初始化
     */
    public function init()
    {
    }
    /**
     * Returns the value of an object property.
     * 返回对象的属性值
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `$value = $object->property;`.
     *
     * 魔术方法，实现 getter
     *
     * @param string $name the property name
     * @return mixed the property value
     * @throws UnknownPropertyException if the property is not defined
     * @throws InvalidCallException if the property is write-only
     * @see __set()
     */
    public function __get($name)
    {
        $getter = 'get' . $name;
        if (method_exists($this, $getter)) {
            // 对象存在 $getter 方法，就直接调用
            return $this->$getter();
        } elseif (method_exists($this, 'set' . $name)) {
            // 如果存在 'set' . $name 方法，就认为该属性是只写的
            throw new InvalidCallException('Getting write-only property: ' . get_class($this) . '::' . $name);
        } else {
            // 否则认为该属性不存在
            throw new UnknownPropertyException('Getting unknown property: ' . get_class($this) . '::' . $name);
        }
    }