iOS 检测字符串中是否含有字母、大写字母、小写字母

检测字符串中是否含有字母：

- (BOOL)containsLetters{
    for (int i = 0; i < self.length; i++) {
        unichar c = [self characterAtIndex:i];
        if(((c > 64)&&(c < 91)) || ((c > 96)&&(c < 123))) {
            return YES;
        }
    }
    return NO;
}

检测字符串中是否含有大写字母：

- (BOOL)containsUpperCaseLetters{
    for (int i = 0; i < self.length; i++) {
        unichar c = [self characterAtIndex:i];
        if((c > 64)&&(c < 91)) {
            return YES;
        }
    }
    return NO;
}

检测字符串中是否含有小写字母：

- (BOOL)containsLowerCaseLetters{
    for (int i = 0; i < self.length; i++) {
        unichar c = [self characterAtIndex:i];
        if((c > 96)&&(c < 123)) {
            return YES;
        }
    }
    return NO;
}