Angular2:返回表达式之间不存在最佳通用类型 [英] Angular2: No best common type exists among return expressions

问题描述

尝试用gulp编译我的打字稿，但会出现以下错误:

Trying to compile my typescript with gulp but I'll get the following error:

返回表达式之间不存在最佳的通用类型.

其中的代码是一个 for 循环，如下所示:

Where the code is a for loop which looks like this:

   getIndexInCompareList(result) {
    for (var i = 0; i < this.compare.length; i++) {
        if (this.compare[i].resource.id == result.resource.id) {
            return i;
        }
    }

    return false;
}

推荐答案

正如@günter-zöchbauer所述，您的函数确实返回两​​种不同的类型.如果您真的想在一种情况下返回数字，否则返回布尔值，则可以使用 any 作为该函数的返回值来解决此问题.

As @günter-zöchbauer mentioned, your function does return two different types. If you really want to return a number in one case and otherwise a boolean you could use any as your return value for the function to fix this issue.

但是，即使没有找到该值，许多其他函数(例如 indexOf )也会返回数字，我建议您也这样做.对于您而言，如果未找到该项目，您还可以返回 -1 .通过这种方式，您可以明确显示自己的类型，还可以为其他人提供清晰的界面.

However, as many other functions such as indexOf return numbers only even if the value was not found I would suggest you do the same. In your case you could also return -1 if the item was not found. This way you can be explicit about your types and also provide a clear interface for others.

function getIndexInCompareList(result): number {
    for (let i = 0; i < this.compare.length; i++) {
        if (this.compare[i].resource.id == result.resource.id) {
            return i;
        }
    }

    return -1;
}

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