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I am designing an iOS app using XCode 4.2's storyboard feature. The app has a login screen that takes a username and password and has a button to log in. Pushing the login button triggers a push seque to another view controller. However, I want the seque to wait until the login comes back successful before proceeding to the next view controller.

I know about prepareForSegue:sender: but heres my issue: the login call is asynchronous. I therefore cannot perform the login there.

Is there someway around this? Can I create a seque in the storyboard that is only triggered when I want it to be (as opposed to when a button is clicked)?

mtmurdock
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3 Answers3

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Ok, I have figured it out. I had defined a segue from a UIButton to the next UIViewController. As defined in this manner, there is no way to conditionally execute the segue.

Instead of putting the segue on the button, I made a segue from the first UIViewController to the other UIViewController. This defines the segue, but associates no action with it. From there I can simply call performSegueWithIdentifier:sender: when I want that segue to execute (in my case being when the async task is complete).

The main advantage of this for me is that IB maintains its structure.

Big thanks to @cli_hlt for pointing me in the right direction (+1).

Scorchio
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mtmurdock
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I don't know if there is a way in IB to perform such an action (although I strongly doubt it) so I suggest to use 

- (void)performSegueWithIdentifier:(NSString *)identifier sender:(id)sender

on the view controller when your asynchronous login signals success.

cli_hlt
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  • Yea I saw that, I was just hoping that there would be some way to do it where I wouldn't have to break the flow in IB. – mtmurdock Nov 21 '11 at 16:10
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You can also call instantiateViewControllerWithIdentifier on an instance of UIStoryBoard. This will return a view controller reference to any point in your storyboard. From there, you can present it however you like and it will pick up the flow of your storyboard.

Scott Ahten
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  • That wouldn't show up in IB though. I was trying to maintain the flowchart on the storyboard. What you are suggesting would not show a link between the two controllers in IB. If you read my answer you'll see how I was able to do essentially the same thing you're proposing while using IB to define the segue. Thanks for the input! +1 – mtmurdock Dec 04 '11 at 04:30