textView的placeholder的书写

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {     if ([text isEqualToString:@"\n"]) {//检测到“完成”         [textView resignFirstResponder];//释放键盘         return NO;     }     if (adviceMsg.text.length==0){//textview长度为0         if ([text isEqualToString:@""]) {//判断是否为删除键             labeltext.hidden=NO;//隐藏文字         }else{             labeltext.hidden=YES;         }     }else{//textview长度不为0         if (adviceMsg.text.length==1){//textview长度为1时候             if ([text isEqualToString:@""]) {//判断是否为删除键                 labeltext.hidden=NO;             }else{//不是删除                 labeltext.hidden=YES;             }             }else{//长度不为1时候             labeltext.hidden=YES;             }     }     return YES; }