dojo.require如果不允许局部变量 [英] dojo.requireIf does not allow local variables

问题描述

我一直在尝试使用本地变量 dojo.require（If），以便根据条件在页面上动态加载模块。

I've been trying to use dojo.require(If) with a local variable to dynamically load a module on a page based on a condition.

// note: dojo v1.4
djConfig = {
  debugAtAllCosts: true
};

示例1（不工作）：

(function() {
  var nameOfClass = "Two";
  dojo.require("my.namespace." + nameOfClass);
  dojo.addOnLoad(function() {
    var oneOrTwo = new my.namespace[nameOfClass]();
  });
}());

错误：ReferenceError：nameOfClass未定义。

Error: ReferenceError: nameOfClass is not defined.

示例2（不工作）

Example 2 (does not work):

(function() {
  var nameOfClass = "Two";
  dojo.requireIf(nameOfClass == "One", "my.namespace.One");
  dojo.requireIf(nameOfClass == "Two", "my.namespace.Two");
  dojo.addOnLoad(function() {
    var oneOrTwo = new my.namespace[nameOfClass]();
  });
}());

错误：ReferenceError：nameOfClass未定义。

Error: ReferenceError: nameOfClass is not defined.

示例3（作品）

Example 3 (works):

(function() {
  window.nameOfClass = "Two";
  dojo.requireIf(window.nameOfClass == "One", "my.namespace.One");
  dojo.requireIf(window.nameOfClass == "Two", "my.namespace.Two");
  dojo.addOnLoad(function() {
    var oneOrTwo = new my.namespace[nameOfClass]();
  });
}());

由于某些原因，它似乎就像require和requireIf只允许其中的全局变量。这是目前的限制，还是我只是做错了？

For some reason, it appears as though require and requireIf only allow global variables inside them. Is that a current limitation, or am I just doing something wrong?

更新1 ：

因此，如果我明白你（@Maine，@jrburke）是否正确，这是debugAtAllCosts的一个限制？如果上述代码构建为跨域（添加xd文件前缀/后缀）并被执行 - 它将按预期工作？

Therefore, if I understand you (@Maine, @jrburke) correctly, this is a limitation of the debugAtAllCosts? If the above code is built as cross-domain (adding the xd file prefix / suffix) and is executed -- it will work as expected?

如果是这种情况，那么本地测试将作为跨域执行的代码的正确方法是什么，而不进行实际构建？

If that is the case, then what is the proper way of locally testing code that will be executed as cross-domain, without making the actual build?

这也让我怀疑预先解析dojo.require的动机。如果loader_xd不会（或者说不能）预解析，为什么为测试/调试创建的方法呢？

That also makes me question the motivation for pre-parsing the dojo.require(s). If the loader_xd will not (or rather can not) pre-parse, why is the method that was created for testing/debugging doing so?

更新2 ：

由于上述更新1中的两个问题与此不相关，我已将其移至分离讨论。

Since the two questions in the Update 1 above are not closely related to this one, I've moved them out into a separate discussion.

推荐答案

这是因为 requireIf 解析正则表达式是第一件事，并在正常程序流程之前执行。

This is because requireIfs are parsed with regexps as the very first thing, and executed before the normal program flow.

如果你要grep Dojo源为requireIf，你应该找到这种行处理它（loader_xd.js）：

If you'll grep Dojo source for requireIf, you should find this kind of lines handling it (loader_xd.js):

var depRegExp = /dojo.(require|requireIf|provide|requireAfterIf|platformRequire|requireLocalization)\s*\(([\w\W]*?)\)/mg;

然后，使用 eval 执行条件全球范围，而不是正常流量的一部分。

The condition is then executed with eval in global scope, and not as a part of normal flow.

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