I have two table views and a detail view being managed by a UINavigationController. When a row is selected on the second table, it pops to a detailed view allowing changes specific data represented by the row. I need to be able to switch between the UITableView and the UIViewController without losing any of the data that might have been changed in the UIViewControllers (button selections, text values entered in fields, etc).
Basically, once the UIViewController is presented, one should be able to switch back and forth between the table and detail view without losing any data.
The problem is, when a UIViewController is popped from the navigation controller, that memory is automatically released, and since I’m using ARC, I can’t just keep a pointer to that with a retain command in the UITableView.
I know that I could manually rebuild the view each time its corresponding table row is selected, but I feel that might be a messy solution. Another option I’ve thought of is keeping an array of pushed UIViewControllers and checking if the selected table row corresponds with an existing value before a new one is created, but that might also get messy.
Any suggestions?
Your final wish in this back and forth of view is what you stated in your question: you want to switch between view controllers without losing any information of the actions performed in these controllers.
But if you think at how MVC pattern works, you should consider a view controller as the glue logic between the view and the model. The view is not persistent, that’s why it is legitimate for ARC to get rid of the owning view controller when the view is no more needed. Instead what you should persist while your app is working is the model data only: the model data will be shared between the involved view controllers, the view controllers will be recreated each time and the corresponding views will be updated based on the model data. The only reason why the view controller should be kept alive is when its alloc-init-loadView takes too much (e.g.: the view is OpenGL backed) but in such case I would suggest you to keep a strong reference to it in the AppDelegate and ask it to refresh the content when the model data is replaced.
So basically what you should do is:
– select the table
– extract the model data associated to the table, including all information relevant for the view controller
– push the view controller; save all view modifications to the model
– when the view controller is popped, the model data will be returned only
– next time, when you push the view controller again, you will restore the model and re-init the view controller.
This approach is not complicated and gives you the possibility to structure the app in a clean way. Tomorrow you can change your view controller structure (that its view and the logic) without any impact in the communication with the other view controllers as this managed by the model passing only.