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

- (void)textFieldDidChanged:(UITextField *)textField {
    NSString *toBeString = textField.text;
    /** 键盘输入模式*/
    NSString *lang = textField.textInputMode.primaryLanguage;
    
    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，有高亮选择的字符串，则暂不对文字进行统计和限制*/
        if (!position) {
            if (toBeString.length > MAX_CHARS) {
                textField.text = [toBeString substringToIndex:MAX_CHARS];
            }
        }
    } 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 > MAX_CHARS) {
            textField.text = [toBeString substringToIndex:MAX_CHARS];
        }
    }
}