- (void)textViewDidChange:(UITextView *)textView{

    NSString *temp=textView.text;

   //字数超过限制数量时，进行截取替换

    if([[textView text] length] > _limitCharactorNumbers){

        textView.text=[temp substringToIndex:_limitCharactorNumbers];

    }

     //显示剩余字数

    _leftNumberLabel.text = [NSString stringWithFormat:@"%u",(_limitCharactorNumbers - textView.text.length)];

    // placeHolder实现方法： 自己添加一个UILabel在UITextView左上角

    if (textView.text.length == 0) {

        _placeHolderLabel.text = _placeHolder;

    }else{

        _placeHolderLabel.text = @"";

    }

}