ios - Tableview显示警报错误

我正在编写一个简单的tableview应用程序，点击该行时会显示警报。

(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    NSString *rowValue =self.greekLetters[indexPath.row];
   // NSString *message=[[NSString alloc] initWithFormat:@"You selected%@!",rowValue];

   if (indexPath.row==0) {
        NSString *message=[[NSString alloc] initWithFormat:@"This is course aaaaa",rowValue];
    }

    if (indexPath.row==1) {
        NSString *message=[[NSString alloc] initWithFormat:@"This is course aaaaa"];
    }


    UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"Course introduction" message:message delegate:nil cancelButtonTitle:@"Return to courses list" otherButtonTitles:nil, nil];

    [alert show];
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

但是，Xcode在这里不喜欢我的if语句，而以下语句有效。

NSString *message=[[NSString alloc] initWithFormat:@"You selected%@!",rowValue];

有人可以在这里给我一个如何使用消息的例子吗？

最佳答案

这是范围的问题。您需要在if语句之前声明消息：

NSString *message;

if (indexPath.row==0) {
    message=[[NSString alloc] initWithFormat:@"This is course aaaaa",rowValue];
}

else if (indexPath.row==1) {
    message=[[NSString alloc] initWithFormat:@"This is course aaaaa"];
}

UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"Course introduction" message:message delegate:nil cancelButtonTitle:@"Return to courses list" otherButtonTitles:nil];

[alert show];
[tableView deselectRowAtIndexPath:indexPath animated:YES];

但是，如果课程号由行号确定，请执行以下操作：

NSString *rowValue =self.greekLetters[indexPath.row];

NSString *message = [[NSString alloc] initWithFormat:@"This is course %@",rowValue];

UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"Course introduction" message:message delegate:nil cancelButtonTitle:@"Return to courses list" otherButtonTitles:nil];

[alert show];
[tableView deselectRowAtIndexPath:indexPath animated:YES];

关于ios - Tableview显示警报错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/27882063/