yii2源码学习笔记(二）

Posted 2020-07-09 dragon16

 yii\base\Component代码详解

<?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 是一个实现属性功能的基类
 * A property is defined by a getter method (e.g. `getLabel`), and/or a setter method (e.g. `setLabel`). For example,
 * 定义了getter和setter方法。例如：
 * the following getter and setter methods define a property named `label`:
 * 
 * ~~~
 * private $_label;
 *
 * public function getLabel()
 * {
 *     return $this->_label;
 * }
 *
 * public function setLabel($value)
 * {
 *     $this->_label = $value;
 * }
 * ~~~
 *
 * Property names are *case-insensitive*.
 * 属性名大小写敏感
 * 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,
 * 可以访问对象的属性，如对象的成员变量。读或写一个属性将导致调用相应的getter或setter方法
 * ~~~
 * // equivalent to $label = $object->getLabel();
 * $label = $object->label;
 * // equivalent to $object->setLabel(‘abc‘);
 * $object->label = ‘abc‘;
 * ~~~
 *
 * If a property has only a getter method and has no setter method, it is considered as *read-only*. In this case, trying
 * to modify the property value will cause an exception.
 * 如果一个属性只有getter方法，就只能读，如果写会出现异常。
 * One can call [[hasProperty()]], [[canGetProperty()]] and/or [[canSetProperty()]] to check the existence of a property.
 * 通过hasProperty canGetProperty或canSetProperty 检查属性是否存在
 * Besides the property feature, Object also introduces an important object initialization life cycle. In particular,
 * creating an new instance of Object or its derived class will involve the following life cycles sequentially:
 * 除了属性特征，对象还引入了一个重要的对象初始化生命周期，
 * 创建一个新的对象或其派生类的实例，将涉及下列生命周期
 * 1. the class constructor is invoked;
 * 2. object properties are initialized according to the given configuration;
 * 3. the `init()` method is invoked.
 *  调用构造函数;
 *  根据给定的对象属性初始化配置;
 *  init()调用的方法.
 * In the above, both Step 2 and 3 occur at the end of the class constructor. It is recommended that
 * you perform object initialization in the `init()` method because at that stage, the object configuration
 * is already applied.
 * 2和3发生在类构造函数的末端。建议
 * 你完成对象的初始化在` init（）`方法因为在那个阶段，对象配置已经应用。
 * In order to ensure the above life cycles, if a child class of Object needs to override the constructor,
 * it should be done like the following:
 * 为了保证的生命周期，如果一个子类的对象需要重写构造函数，
 * ~~~
 * public function __construct($param1, $param2, ..., $config = [])
 * {
 *     ...
 *     parent::__construct($config);
 * }
 * ~~~
 *
 * 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.
 * 一个配置的参数应该声明为最后一个参数，构造函数和父类的实现应该在结尾调用
 * @author Qiang Xue <[email protected]>
 * @since 2.0
 */
class Object
{
    /**
     * 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
     * @return string the fully qualified name of this class.
     */
    public static function className()
    {   //哪个类调用，就返回哪个类，
        return get_called_class();
    }

    /**
     * Constructor.
     * The default implementation does two things:
     *
     * - Initializes the object with the given configuration `$config`.
     * - Call [[init()]].
     *
     * If this method is overridden in a child class, it is recommended that
     *
     * - the last parameter of the constructor is a configuration array, like `$config` here.
     * - call the parent implementation at the end of the constructor.
     *
     * @param array $config name-value pairs that will be used to initialize the object properties
     */
    public function __construct($config = [])
    {
        //根据$config初始化对象
        if (!empty($config)) {
            Yii::configure($this, $config);
        }
        //调用 init（）方法，用于初始化，可以被重写。
        $this->init();
    }

    /**
     * Initializes the object.
     * This method is invoked at the end of the constructor after the object is initialized with the
     * given configuration.
     * 初始化结束时调用，与给定的配置初始化。
     */
    public function init()
    {
    }

    /**
     * Returns the value of an object property.
     *
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `$value = $object->property;`.
     * 不要直接调用这个方法,因为它是一个PHP魔术方法，要隐式调用
     * @param string $name the property name 属性名称
     * @return mixed the property value      属性值
     * @throws UnknownPropertyException if the property is not defined 属性未定义
     * @throws InvalidCallException if the property is write-only   该属性写
     * @see __set()
     */
    public function __get($name)
    {
        $getter = ‘get‘ . $name;//定义$getter
        if (method_exists($this, $getter)) {
            return $this->$getter();//存在方法，直接调用
        } elseif (method_exists($this, ‘set‘ . $name)) {
            // 如果存在 ‘set‘ . $name 方法，就认为属性是只写
            throw new InvalidCallException(‘Getting write-only property: ‘ . get_class($this) . ‘::‘ . $name);
        } else {
            // 否则认为该属性不存在 未定义
            throw new UnknownPropertyException(‘Getting unknown property: ‘ . get_class($this) . ‘::‘ . $name);
        }
    }

    /**
     * Sets value of an object property.
     *
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `$object->property = $value;`.
     * @param string $name the property name or the event name 属性或事件名称
     * @param mixed $value the property value   属性值
     * @throws UnknownPropertyException if the property is not defined 未定义属性
     * @throws InvalidCallException if the property is read-only    属性只写
     * @see __get()
     */
    public function __set($name, $value)
    {
        $setter = ‘set‘ . $name;
        if (method_exists($this, $setter)) {
            $this->$setter($value);//对象存在$setter方法，直接调用
        } elseif (method_exists($this, ‘get‘ . $name)) {
             // 存在 ‘get‘ . $name 方法，就认为该属性是只读
            throw new InvalidCallException(‘Setting read-only property: ‘ . get_class($this) . ‘::‘ . $name);
        } else {  // 否则认为该属性不存在 未定义
            throw new UnknownPropertyException(‘Setting unknown property: ‘ . get_class($this) . ‘::‘ . $name);
        }
    }

    /**
     * Checks if the named property is set (not null).
     * 检查属性是否设置
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `isset($object->property)`.
     *
     * Note that if the property is not defined, false will be returned. 未定义返回false
     * @param string $name the property name or the event name  属性名
     * @return boolean whether the named property is set (not null).    
     */
    public function __isset($name)
    {
        $getter = ‘get‘ . $name;
        if (method_exists($this, $getter)) {
            //由$getter获取的值不为null，该属性存在，返回true
            return $this->$getter() !== null;
        } else {
            return false;//该属性存在，返回false
        }
    }

    /**
     * Sets an object property to null.
     * 设置一个属性为空
     * Do not call this method directly as it is a PHP magic method that
     * will be implicitly called when executing `unset($object->property)`.
     *
     * Note that if the property is not defined, this method will do nothing.
     * If the property is read-only, it will throw an exception.
     * @param string $name the property name    属性名
     * @throws InvalidCallException if the property is read only. 属性只读
     */
    public function __unset($name)
    {
        $setter = ‘set‘ . $name;
        if (method_exists($this, $setter)) {
            //如果存在，由$setter设置为null
            $this->$setter(null);
        } elseif (method_exists($this, ‘get‘ . $name)) {
            //如果是只读的，抛出异常
            throw new InvalidCallException(‘Unsetting read-only property: ‘ . get_class($this) . ‘::‘ . $name);
        }
    }

    /**
     * Calls the named method which is not a class method.
     * 调用指定的方法而不是一个类方法.
     * 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.
     * @param string $name the method name  方法名
     * @param array $params method parameters 方法参数
     * @throws UnknownMethodException when calling unknown method 调用未知方法
     * @return mixed the method return value    
     */
    public function __call($name, $params)
    {
        //调用指定方法
        throw new UnknownMethodException(‘Calling unknown method: ‘ . get_class($this) . "::$name()");
    }

    /**
     * Returns a value indicating whether a property is defined.
     * A property is defined if:
     *
     * - the class has a getter or setter method associated with the specified name
     *   (in this case, property name is case-insensitive);
     * - the class has a member variable with the specified name (when `$checkVars` is true);
     * 检查查对象或类是否具有 $name 属性，如果 $checkVars 为 true，则不局限于是否有 getter或setter
     * @param string $name the property name    属性名
     * @param boolean $checkVars whether to treat member variables as properties 是否将成员变量作为属性对待 true/false
     * @return boolean whether the property is defined  属性是否定义
     * @see canGetProperty()
     * @see canSetProperty()
     */
    public function hasProperty($name, $checkVars = true)
    {
        return $this->canGetProperty($name, $checkVars) || $this->canSetProperty($name, false);
    }

    /**
     * Returns a value indicating whether a property can be read.
     * 返回一个值指示是否可以读取属性.
     * A property is readable if:
     *
     * - the class has a getter method associated with the specified name
     *   (in this case, property name is case-insensitive);
     * - the class has a member variable with the specified name (when `$checkVars` is true);
     * 检查对象或类是否能够获取 $name 属性，如果 $checkVars 为 true，则不局限于是否有 getter
     * @param string $name the property name
     * @param boolean $checkVars whether to treat member variables as properties
     * @return boolean whether the property can be read
     * @see canSetProperty()
     */
    public function canGetProperty($name, $checkVars = true)
    {
        //是否存在该属性
        return method_exists($this, ‘get‘ . $name) || $checkVars && property_exists($this, $name);
    }

    /**
     * Returns a value indicating whether a property can be set.
     * 属性是否可设置
     * A property is writable if:
     *
     * - the class has a setter method associated with the specified name
     *   (in this case, property name is case-insensitive);
     * - the class has a member variable with the specified name (when `$checkVars` is true);
     * 检查对象或类是否能够设置 $name 属性，如果 $checkVars 为 true，则不局限于是否有 setter
     *
     * @param string $name the property name
     * @param boolean $checkVars whether to treat member variables as properties    是否将成员变量作为属性来对待
     * @return boolean whether the property can be written  是否可写
     * @see canGetProperty()
     */
    public function canSetProperty($name, $checkVars = true)
    {
        return method_exists($this, ‘set‘ . $name) || $checkVars && property_exists($this, $name);
    }

    /**
     * Returns a value indicating whether a method is defined.
     * 方法是否定义
     * The default implementation is a call to php function `method_exists()`.
     * You may override this method when you implemented the php magic method `__call()`.
     * @param string $name the method name
     * @return boolean whether the method is defined    是否具有 $name 方法
     */
    public function hasMethod($name)
    {
        return method_exists($this, $name);
    }
}