从子类调用超类方法 - JavaScript
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Calling Superclass Method From Subclass - JavaScript
提问by Altherat
Possible Duplicate:
set attribute with javascript super method
可能的重复：
使用 javascript 超级方法设置属性
I am trying to create a simple game in HTML5 for fun. I have an Entity class that is supposed to be the superclass of the Player class.
我正在尝试用 HTML5 创建一个简单的游戏来获得乐趣。我有一个实体类，它应该是 Player 类的超类。
function Entity(x, y) {
this.x = x;
this.y = y;
this.tick = function() {
//Do generic stuff
}
}
function Player(x, y) {
this.parent.constructor.call(this, x, y);
this.tick = function() {
//Do player-specific stuff
this.parent.tick.call(this);
}
}
Player.prototype = new Entity();
Player.prototype.constructor = Player;
Player.prototype.parent = Entity.prototype;
The problem is at this line:
问题出在这一行：
this.parent.tick.call(this);
I get an error displayed in the JavaScript console of chrome: "Uncaught TypeError: Cannot call method 'call' of undefined".
我在 chrome 的 JavaScript 控制台中显示错误：“未捕获的类型错误：无法调用未定义的方法‘调用’”。
I don't get it and I've spent a long time trying to find posts of a similar issue. My call to the superclass' constructor works fine but the call to the superclass' tick method does not work.
我不明白，我花了很长时间试图找到类似问题的帖子。我对超类'构造函数的调用工作正常，但对超类'tick 方法的调用不起作用。
I'm very new to making games so I have no idea if this a good setup (calling superclass tick from subclass tick). If there is a better, more typical way that people use, please tell.
我对制作游戏很陌生，所以我不知道这是否是一个好的设置（从子类 tick 调用超类 tick）。如果有更好的、更典型的人们使用的方式，请告诉。
Thanks.
谢谢。
回答by Bergi
Adapting this answerto your code:
将此答案调整为您的代码：
function Entity(x, y) {
this.x = x;
this.y = y;
this.tick = function() {
//Do generic stuff
}
}
function Player(x, y) {
this.parent.constructor.call(this, x, y);
var oldtick = this.tick;
this.tick = function() {
//Do player-specific stuff
oldtick.call(this);
}
}
Player.prototype = Object.create(Entity.prototype);
Player.prototype.constructor = Player;
Player.prototype.parent = Entity.prototype;
回答by Mark
Your question inspired me to look around and I found what I think is a great article by Josh Gertzenabout this concept.
你的问题激励我环顾四周，我发现我认为是Josh Gertzen关于这个概念的一篇很棒的文章。
I blatantly copy from his article some code to set up an extendsmethod on classes:
我公然从他的文章中复制了一些代码来设置extends类的方法：
function Class() { }
Class.prototype.construct = function() {};
Class.extend = function(def)
{
var classDef = function()
{
if (arguments[0] !== Class)
{
this.construct.apply(this, arguments);
}
};
var proto = new this(Class);
var superClass = this.prototype;
for (var n in def)
{
var item = def[n];
if (item instanceof Function) item.$ = superClass;
proto[n] = item;
}
classDef.prototype = proto;
classDef.extend = this.extend;
return classDef;
};
After which your case is as simple as:
之后，您的情况就像这样简单：
var Entity = Class.extend({
tick: function()
{
alert('Entity tick');
}
});
var Player = Entity.extend({
tick: function()
{
alert('Player tick');
arguments.callee.$.tick.call(this);
}
});
p = new Player();
p.tick();
Which will alert Player tickand then Entity tick.
哪个会发出警报Player tick，然后Entity tick。
