Google Closure使用this关键字绑定/解决问题

Question

什么是Google Closure解决thisJavaScript回调函数中关键字问题的解决方案.它在OO风格编程中非常有用.

在Google Closure中是否存在OOP的约定或样式？

更新 如何在ViewportSizeMonitor处理程序中访问this.darklayer ???

    goog.require('goog.dom');
goog.require('goog.events');
goog.require('goog.events.EventType');
goog.require('goog.math.Size');
goog.require('goog.style');

goog.require('goog.dom.ViewportSizeMonitor');

goog.provide('ehsun7b.ajax.AjaxBox');

ehsun7b.ajax.AjaxBox = function (url, containerClass) {
  try {
    this.url = url;
    this.containerClass = containerClass;

    var viwportSize = goog.dom.getViewportSize();
    this.darklayer = goog.dom.createDom("div", {
      "style": "width: " + viwportSize.width + "px;" + "height: " + 
      viwportSize.height + "px;" +
      "background-image: url('css/img/50black.png');" +
      "z-index: 1000;" +
      "position: absolute;" +
      "left: 0px; top: 0px;"
    });

    var vsm = new goog.dom.ViewportSizeMonitor();
    goog.events.listen(vsm, goog.events.EventType.RESIZE, function(e) {
      console.log("this: " + this.darklayer);
    });

    this.container = goog.dom.createDom("div", {
      "class": this.containerClass
    });    
    goog.dom.appendChild(this.darklayer, this.container);
    goog.dom.setTextContent(this.container, "hello ajax box");    

    this.show = function() {
      goog.dom.appendChild(document.body, this.darklayer);
    },

    this.hide = function() {    
      goog.dom.removeNode(this.darklayer);
    }
  } catch (e) {
    console.log("error: " + e);
  }
};

我按照Closure的风格改变了我的课程:

goog.require('goog.dom');
goog.require('goog.events');
goog.require('goog.events.EventType');
goog.require('goog.math.Size');
goog.require('goog.style');

goog.require('goog.dom.ViewportSizeMonitor');

goog.provide('ehsun7b.ajax.AjaxBox');

ehsun7b.ajax.AjaxBox = function (url, containerClass) {
  try {
    this.url = url;
    this.containerClass = containerClass;

    var viwportSize = goog.dom.getViewportSize();
    this.darklayer = goog.dom.createDom("div", {
      "style": "width: " + viwportSize.width + "px;" + "height: " + 
      viwportSize.height + "px;" +
      "background-image: url('css/img/50black.png');" +
      "z-index: 1000;" +
      "position: absolute;" +
      "left: 0px; top: 0px;"
    });

    var vsm = new goog.dom.ViewportSizeMonitor();
    goog.events.listen(vsm, goog.events.EventType.RESIZE, function(e) {
      console.log("this: " + this.darklayer);
    });

    this.container = goog.dom.createDom("div", {
      "class": this.containerClass
    });    
    goog.dom.appendChild(this.darklayer, this.container);
    goog.dom.setTextContent(this.container, "hello ajax box");                   
  } catch (e) {
    console.log("error: " + e);
  }
};

ehsun7b.ajax.AjaxBox.prototype.show = function() {
  goog.dom.appendChild(document.body, this.darklayer);
}

ehsun7b.ajax.AjaxBox.prototype.hide = function() {    
  goog.dom.removeNode(this.darklayer);
}

Answer 1

goog.bind是通用解决方案.例如:

goog.bind(this.someFunction, this);
goog.bind(this.someFunction, this, arg1);
goog.bind(this.someFunction, this, arg1, arg2);

框架通常设计为可以避免这种情况,因此不必显式调用goog.bind.

例如,goog.events.EventHandler自动将回调绑定到您在其构造函数中设置的处理程序.

var handler = new goog.events.EventHandler(this);
handler.listen(something, 'something', this.someFunction); // no need to bind

数组函数还支持处理程序参数.

goog.array.forEach(elements, this.someFunction, this);
var items = goog.array.map(elements, this.someFunction, this);

等等.框架的大多数部分都很容易做到这一点,它非常适合"伪经典"继承.

有关更多详细信息,请参阅http://www.bolinfest.com/javascript/inheritance.php