View Controllers and code completion - ios

Question

My app takes a picture and then needs to ask the user what they want to name their image.
I've tried using UIAlertView, but I'm having this issue where the string itself isn't collected on time because the code doesn't pause to wait for user input.
What I want to try now is to make a new view controller that just has a text field for the user to input their PDF file's name. What I want to know is how exactly it would conceptually work (or if it would work at all).
Pseudo code:
1. The user clicks on a take picture button, which runs a method that captures the image.
2. After the image is in memory, the View Controller that has the text field is presented.
3. The user inputs the information into the text field
4. The view is dismissed
5. The code in the method that captures the image continues.
Is this how view controllers work? If I present a view controller in from a button, and then dismiss the presented view controller from another button in the new view controller, does the code in the original method continue executing where it left off?

Answer 1

No. The code in the original method executes immediately after presenting the UIAlertView (or UIActionSheet, or any other thing). It doesn't wait for the dismissal.
To handle event of dismissing the UIAlertView, for example there is mechanism called Delegation. It works like this:
You create the UIAlertView in View Controller.
You set UIAlertView's .delegate property to some object. Typically the View Controller itself. That object should implement several methods, that UIAlertViewDelegate defines.
You present the Alert and your code continues immediately.
When user click on some button, the UIAlertView calls one of the defined methods on its Delegate. In our case, the View Controller, which brings us back to our code.
In your delegate method, you “continue” what you wanted to do before Alert was presented.
Example code:
- (void)presentAlert {
// 1
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Hello!"
message:nil
delegate:self // 2
cancelButtonTitle:#"Eh?"
otherButtonTitles:#"Hello!", #"Hi!", #"Aloha!" nil];
[alert show]; // 3
NSLog(#"Did present alert"); // immediately executed
}
// Between these method calls may pass several seconds, minutes or eternity.
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
// 4, 5
NSLog(#"Did click button %#", [alertView buttonTitleAtIndex:buttonIndex]);
}
In addition, you will have to declare UIAlertViewDelegate protocol on your View Controller:
#interface YourViewController : UIViewController <UIAlertViewDelegate>

Answer 2

I believe you are misunderstanding Viewcontrollers quite a bit. But i cannot explain all the issues here, or this post would turn into a book. So heres a very helpful link (that i hope you already did read) and a few hints:
https://developer.apple.com/library/ios/featuredarticles/viewcontrollerpgforiphoneos/Introduction/Introduction.html
Viewcontrollers are presented either modally (stacked on top of each other) or in a common ParentViewController (such as a NavigationController or a SlideViewController). The presenting controller will always either keep the controller running in the background or finish the Viewcontrollers logic before presenting a new one. So the shortest possible answr to your question is no.
Pay special attention to the Viewcontroller lifecycle. ViewControllers have special callback methods that get invoked under certain circumstances. Look out for the viewDidLoad and viewDidAppear - methods, this will clear your confusion quite a bit.
Last, not least, look into the delegate pattern. Delegates are a way of sending messages between viewcontrollers. So you could make the ViewController that takes the name send a message with the chosen name to the viewController that took the picture.
Heres a link to the delegate programming guide:
https://developer.apple.com/library/ios/documentation/general/conceptual/CocoaEncyclopedia/DelegatesandDataSources/DelegatesandDataSources.html
i hope that gets you started