可选类型'$ T11'不能用作布尔值;自从安装XCode 6 beta 7后测试'！= nil' [英] Optional type '$T11' cannot be used as a boolean; test for '!= nil' instead since installing XCode 6 beta 7

问题描述

以下是我收到错误的代码：

for (key, value) in info {
    let fieldValue: AnyObject? = value

    if (!fieldValue || fieldValue?.length == 0) { // this line gives the error
        informationComplete = false;
    } 
}

这就是XCode建议我使用哪个导致另一个错误：

for (key, value) in info {
    let fieldValue: AnyObject? = value

    if ((!fieldValue || fieldValue?.length == 0) != nil) { //bool not convertible to string
        informationComplete = false;
    }
 }

感谢帮助。

感谢您的时间

推荐答案

选项不再被视为布尔表达式（如Swift中所述）参考 - 修订历史记录）：

Optionals are no longer considered boolean expression (as stated in the Swift Reference - Revision History):

Optionals在有值时不再隐式评估为true，如果没有，则不再为false使用可选的Bool值时避免混淆。相反，使用==或！=运算符对nil进行显式检查，以确定可选项是否包含值。

Optionals no longer implicitly evaluate to true when they have a value and false when they do not, to avoid confusion when working with optional Bool values. Instead, make an explicit check against nil with the == or != operators to find out if an optional contains a value.

so你必须明确如下：

so you have to make it explicit as follows:

if (fieldValue == nil || ...

我记得在测试版6中有所改变 - 你使用的是beta 5吗？

I remember that changed in beta 6 - were you using beta 5?

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