IOS：以代碼形式顯示登錄屏幕的代碼

Question

我想用登錄屏幕（和首次使用的加入屏幕）對應用程序進行密碼保護。 SO上的一些答案建議測試用戶是否以初始屏幕的外觀出現在viewdid中，如果沒有登錄則以模態方式顯示登錄屏幕。

我試過了，但是代碼不起作用。 有人知道用於呈現模態視圖控制器的最新代碼嗎？ 注意我在情節提要中創建了登錄屏幕，並為其指定了情節提要ID“ login”。

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    //if not logged in, modally present login screen here.

    if(![[NSUserDefaults standardUserDefaults] boolForKey:@"loggedIn"]) {
        // go to login screen
        NSLog(@"not logged in");//this fires so logic is ok
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
        UIViewController *ivc = [storyboard instantiateViewControllerWithIdentifier:@"login"];//this line gives warning it is not being used
    } else {
        // go to main screen
    }
} 
/*perhaps I should call this somewhere?

- (void)presentModalViewController:(UIViewController *)modalViewController animated:(BOOL)animated
*/

Answer 1

感謝@rdelmar的評論，您必須具有presentViewController:animated:completion: (presentModalViewController:animated:該ivc。

- (void)viewDidAppear:(BOOL)animated
{
   [super viewDidAppear:animated];
   //if not logged in, modally present login screen here.

   if(![[NSUserDefaults standardUserDefaults] boolForKey:@"loggedIn"]) {
       // go to login screen
       NSLog(@"not logged in");//this fires so logic is ok
       UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
       UIViewController *ivc = [storyboard instantiateViewControllerWithIdentifier:@"login"];//LOOK AT NEXT LINE
       [self presentViewController:ivc animated:YES completion:nil]; //THIS LINE IS MISSING.
  } else {
    // go to main screen
  }
}