1，首先我们需要控制输入字符的验证，比如（中国的）手机号不能超过11位人，验证码为4/6位 密码多少位等。。。

[_nameText addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
[_phoneText addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
[_textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

实现textFieldDidChange方法，判断中文下输入

pragma mark – 输入框观察者事件

• (void)textFieldDidChange:(UITextField *)textField {
  NSInteger kMaxLength = 10 ;
  NSString *toBeString = textField.text;
  if (textField == _phoneText) {
  kMaxLength = 11;
  }else if (textField == _nameText){
  kMaxLength = 12;
  }else if (textField == _textField){
  kMaxLength = 5;
  }
  NSString *lang = [[UIApplication sharedApplication]textInputMode].primaryLanguage; //ios7之前使用[UITextInputMode currentInputMode].primaryLanguage
  if ([lang isEqualToString:@"zh-Hans"]) { //中文输入
  UITextRange *selectedRange = [textField markedTextRange];
  //获取高亮部分
  UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
  if (!position) {// 没有高亮选择的字，则对已输入的文字进行字数统计和限制
  if (toBeString.length > kMaxLength) {
  textField.text = [toBeString substringToIndex:kMaxLength];
  }
  }
  }else{//中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
  if (toBeString.length > kMaxLength) {
  textField.text = [toBeString substringToIndex:kMaxLength];
  }
  }
  self.sureBtn.userInteractionEnabled = YES;
  }

3，提交的时候用正则表达式验证：
if ([self.phoneText.text length] == 0) {
[DZTools showNOHud:LocalizedString(@"请输入电话号码") delay:1];
return;
}
///13456789{9} 正则表达式
if (![self.phoneText.text isTelephone]) {
[DZTools showNOHud:LocalizedString(@"请输入正确的电话号码") delay:1];
return;
}