Question

我无法将此Block代码从Objective C转换为Swift。我在网上搜索了一些例子但没有修复我得到的错误。

任何帮助都将不胜感激。

- (void)didReceiveMemoryWarning {
    [[self.viewControllersByIdentifier allKeys] enumerateObjectsUsingBlock:^(NSString *key, NSUInteger idx, BOOL *stop) {
        if (![self.destinationIdentifier isEqualToString:key]) {
            [self.viewControllersByIdentifier removeObjectForKey:key];
        }
    }];
    [super didReceiveMemoryWarning];
}

以下是我的尝试：

override func didReceiveMemoryWarning() {
    var array : NSArray = self.viewControllersByIdentifier.allKeys
    array.enumerateObjectsUsingBlock { (key, idx, stop) in
        if (![self.destinationIdentifier == key]) {
            self.viewControllersByIdentifier .removeObjectForKey(key)
        }
    }
    super.didReceiveMemoryWarning()
}

我得到的错误是在“if”语句中，它告诉我“String不能转换为”MirrorDisposition“。

Answer 1

你在Swift中留下了一些Objective-C（一些流氓方括号）：

if(![self.destinationIdentifier == key]) {

但是，您可能会发现使用Swift的for-in比array.enumerateObjectsUsingBlock更容易：

override func didReceiveMemoryWarning() {
    for key in self.viewControllersByIdentifier.allKeys {
        // note key will be an AnyObject so you need to cast it to an appropriate type… 
        // also, this means you can use != rather than ! and ==
        if self.destinationIdentifier != key as? NSString {
            self.viewControllersByIdentifier.removeObjectForKey(key)
        }
    }
    super.didReceiveMemoryWarning()
}

Answer 2

你看过文档了吗？

func enumerateObjectsUsingBlock(_ block: (AnyObject!,
                                     Int,
                                     UnsafeMutablePointer<ObjCBool>) -> Void)

我如何在Swift中使用enumerateObjectsUsingBlock

2 个答案: