iphone - 检测字符是字母还是数字

Question

在 objective-c 中，我如何检查单个字符是字母还是数字？我想消除所有其他字符。

Answer 1

消除非字母:

NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
NSCharacterSet *notLetters = [[NSCharacterSet characterSetWithCharactersInString:letters] invertedSet];
NSString *newString = [[string componentsSeparatedByCharactersInSet:notLetters] componentsJoinedByString:@""];

一次检查一个字符:

for (int i = 0; i < [string length]; i++) {
    unichar c = [string characterAtIndex:i];
    if ([notLetters characterIsMember:c]) { 
       ... 
    }
}