objective-c - Cocoa 中处理字符串的整数转换

Question

我希望这是一个非常简单的问题。我只是想将 char 转换为小写版本。这是我的代码:

- (IBAction)click:(id)sender { 
    [outputLabel setText:[inputField text]];
    NSString* textFieldString = [inputField text];
    NSLog(@"String is %@", textFieldString);
    int textFieldLength = textFieldString.length;
    UniChar* currChar = [textFieldString characterAtIndex:0];
    NSLog(@"First char is %c", currChar);
    NSLog(@"Length is %i", textFieldLength);
    //currChar = [currChar lowercaseString];
    //NSLog(@"Lowercase char is %c", currChar);
}

它给了我以下错误:

Initialization makes pointer from integer without a cast on the line:
NSString* currChar = [textFieldString characterAtIndex:0];

但是，在查看文档时，它说方法 characterAtIndex: 返回一个字符，而不是整数。给出了什么？

Answer 1

characterAtIndex 返回 unichar，它是一个无符号短整型。该行应该是

unichar currChar = [textFieldString characterATtIndex:0];

此外，您可以使用 lowercaseString 来获取整个 NSString 的小写:

NSString *lowercase = [textFieldString lowercaseString];