说明:
^.*[\u4e00-\u9fa5].*$ 是否包含中文
^[\u4E00-\u9FA5]+$  是否全中文
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (![string isEqualToString:@""]) {
        if ([self isChinese:string]) {
            return NO;
        }
    }
    return YES;
}
- (BOOL)isChinese:(NSString *)string {
    NSString *regex = @"^[\u4E00-\u9FA5]+$";
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
    
    BOOL isMatch = [pred evaluateWithObject:string];
    return isMatch;
}