- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{ NSInteger existedLength = textField.text.length; NSInteger selectedLength = range.length; NSInteger replaceLength = string.length; NSInteger pointLength = existedLength - selectedLength + replaceLength; //超過16位 就不能在輸入了 if (pointLength > 16) {  return NO; }else{  return YES; } } 

 -(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text{ //這個判斷相當于是textfield中的點擊return的代理方法 if ([text isEqualToString:@"/n"]) {  [textView resignFirstResponder];  return NO; }  //在輸入過程中 判斷加上輸入的字符 是否超過限定字數 NSString *str = [NSString stringWithFormat:@"%@%@", textView.text, text]; if (str.length > 500) {  textView.text = [textView.text substringToIndex:500];  return NO; } return YES;}