- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

 if ([self isInputRuleAndNumber:string] || [string isEqualToString:@""]) {
  return YES;
 }
 return NO;
}

 [textField addTarget:self action:@selector(textFieldChanged:) forControlEvents:UIControlEventEditingChanged];

- (void)textFieldChanged:(UITextField *)textField {

 NSString *toBeString = textField.text;
 NSString *lastString;
 if(toBeString.length>0)
  lastString=[toBeString substringFromIndex:toBeString.length-1];

 if (![self isInputRuleAndNumber:toBeString]&&[self hasEmoji:lastString]) {
  textField.text = [self disable_emoji:toBeString];
  return;
 }
 NSString *lang = [[textField textInputMode] primaryLanguage];
 if([lang isEqualToString:@"zh-Hans"]) {
  UITextRange *selectedRange = [textField markedTextRange];
  UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
  if(!position) {
   NSString *getStr = [self getSubString:toBeString];
   if(getStr && getStr.length > 0) {
    textField.text = getStr;
   }
  }
 } else{
  NSString *getStr = [self getSubString:toBeString];
  if(getStr && getStr.length > 0) {
   textField.text= getStr;
  }
 }
}

- (BOOL)isInputRuleAndNumber:(NSString *)str {
 NSString *pattern = @"[a-zA-Z\u4E00-\u9FA5\\u0030-\\u0039]";
 NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", pattern];
 BOOL isMatch = [pred evaluateWithObject:str];
 return isMatch;
}

- (BOOL)hasEmoji:(NSString*)str{
 NSString *pattern = @"[^\\u0020-\\u007E\\u00A0-\\u00BE\\u2E80-\\uA4CF\\uF900-\\uFAFF\\uFE30-\\uFE4F\\uFF00-\\uFFEF\\u0080-\\u009F\\u2000-\\u201f\r\n]";
 NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", pattern];
 BOOL isMatch = [pred evaluateWithObject:str];
 return isMatch;
}

#define kMaxLength 20;
-(NSString *)getSubString:(NSString*)string
{
 NSStringEncoding encoding = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
 NSData* data = [string dataUsingEncoding:encoding];
 NSInteger length = [data length];
 if (length > kMaxLength) {
  NSData *data1 = [data subdataWithRange:NSMakeRange(0, kMaxLength)];
  NSString *content = [[NSString alloc] initWithData:data1 encoding:encoding];
  if (!content || content.length == 0) {
   data1 = [data subdataWithRange:NSMakeRange(0, kMaxLength - 1)];
   content = [[NSString alloc] initWithData:data1 encoding:encoding];
  }
  return content;
 }
 return nil;
}