IOS UITextField－持续更新

限制textField长度

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

#define kMaxLength 10
-(void)textFiledEditChanged:(NSNotification *)obj{
    [self setNeedsStatusBarAppearanceUpdate];

    UITextField *textField = (UITextField *)obj.object;

    NSString *toBeString = textField.text;
    NSString *lang = [[[UITextInputMode activeInputModes] firstObject]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];
            }
        }
        // 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
    else{
        if (toBeString.length > kMaxLength) {
            textField.text = [toBeString substringToIndex:kMaxLength];
        }
    }

}