接收通知

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFiledEditChanged:) name:@"UITextFieldTextDidChangeNotification" object:nil];

通知方法

-(void)textFiledEditChanged:(NSNotification *)obj{
    UITextField *textField = (UITextField *)obj.object;
    int kMaxLength = 10;
    NSString *toBeString = textField.text;
    NSString *lang = [[UITextInputMode currentInputMode] primaryLanguage]; // 键盘输入模式
    if ([lang isEqualToString:@"zh-Hans"]) { // 简体中文输入，包括简体拼音，健体五笔，简体手写
        UITextRange *selectedRange = [textField markedTextRange];
        //获取高亮部分
        UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
        // 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 (!position) {
            if (toBeString.length > kMaxLength) {
                textField.text = [toBeString substringToIndex:kMaxLength];
             }
         }else{
             // 有高亮选择的字符串，则暂不对文字进行统计和限制
         }
     }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];
         }
      }
     _noticeStr = textField.text;
}