objective-c - 初始化变量并在 for 循环中更改其值后访问它

Question

我正在尝试将这段 Objective-C 代码翻译成 Swift:

- (void) performActivity{
NSMutableString *reversedStrings = [[NSMutableString alloc] init];
for (NSString *string in self.activityItems){
    [reversedStrings appendString:[self reverseOfString:string]];
    [reversedStrings appendString:@"\n"];
}
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Reversed"
                                                    message:reversedStrings
                                                   delegate:self
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles:nil];
[alertView show];

}

我的 Swift 代码是:

override func performActivity() {

    var reversedStrings = String()

    for string in activityItems{

        reversedStrings += reverseOfString(string)
        reversedStrings += "\n"
    }

    var alert = UIAlertView(title: "Reversed",
        message: reversedStrings,
        delegate: self,
        cancelButtonTitle: "Cancel",
        otherButtonTitles: "Ok")

    alert.show()
}

但我的警报中的消息仍然是空字符串。如何访问 for 循环的结果reverseStrings？预先感谢您的回答。

Answer 1

您的 reverseOfString() 实现很可能无法正常工作。这是一个可行的解决方案:

var reversedStrings = String()

for string in activityItems{

    reversedStrings += string.reverse()
    reversedStrings += "\n"
}

它使用String扩展实现reverse方法:

extension String {
    func reverse() -> String {
        var result = ""

        for character in self {
            result = "\(character)" + result
        }

        return result
    }
}