使用功能设置对象成员失败 [英] Setting members of object using function fails

问题描述

我正在尝试对我正在创建的游戏实施一种多人游戏扩展.在XMLHttpRequest之后，将返回游戏ID，即多人游戏会话的ID.

I'm trying to implement a kind of multiplayer extension to a game I'm creating. After a XMLHttpRequest, a game ID is returned, i.e. the ID of a multiplayer session.

我正在使用以下代码，其中Multiplayer是静态类:

I'm using the following code, in which Multiplayer is a static class:

var Multiplayer = {
    baseURL: 'http://127.0.0.1:8888/m',
    gameID: -1,

    create:
    function() {
        $.get(this.baseURL, {'a':'c'}, function(text) {
            this.gameID = parseInt(text);
        });
    }
}

失败，因为似乎无法使用this.gameID = parseInt(text).当我将其更改为Multiplayer.gameID = parseInt(text)时，它就像一个吊饰.

It fails, because it seems this.gameID = parseInt(text) cannot be used. When I change it to Multiplayer.gameID = parseInt(text), it works like a charm.

this.gameID似乎是未定义的，而Multiplayer.gameID可以被读写.

It seems like this.gameID is undefined, while Multiplayer.gameID can both be written to and read from.

这是正确的吗?如果是这样，为什么会这样?

Is this correct and if so, why is this the case?

推荐答案

Javascript没有类，并且this的行为与您期望的来自C ++或Java背景无关.尝试将您的创建函数更改为此:

Javascript doesn't have classes, and this does not behave as you expect coming from a C++ or Java background. Try changing your create function to this:

function() {
    var that = this;
    $.get(this.baseURL, {'a':'c'}, function(text) {
        that.gameID = parseInt(text);
    });
}

关键点在于，每个function()都使用特定的this值调用，并且它可能与封闭函数的值不同.

The key points are that every function() is invoked with a particular this value, and it may not be the same value as the enclosing function's.

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