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Editorial Team
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Asked: 2026-06-04T01:26:33+00:00

I am new to iOS programming, i read the view controller programming guide but

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I am new to iOS programming, i read the view controller programming guide but some things are still unclear to me

  • View of a viewcontroller is destroyed but viewcontroller remains, there nothing specified regarding if I my self want to destroy any viewcontroller or I just missed it. VC guide says iOS destroy VC when memory start getting short for other resources and same goes for VC’s view right? Need to understand memory management of VC, please read my second point.

  • In a uinavigationcontroller i have a tableviewcontroller which display list of my friends, on selecting any of my friend i am pushing another VC of chat. The problem is every time on selecting a friend do i have to create a new instance of chat VC? how this chat VC will be unique for every friend i am trying to chat with? I am also saving messages in DB so who ever friend window open or close messages shows up, user don’t get a blank view. Is it possible only one instant of chat VC is used for every friend uniquely(means only message of particular friend show and send to him to whom i am trying to chat). I think this problem is related to passing data between viewcontrollers but i am confused.

I hope i have clearly define what i am confused in. Please ignore any silly mistakes.

Thank you.

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1 Answer

  1. Editorial Team

    Answer to your queries –

    1. View of a viewcontroller is destroyed but view controller remains

    According to UIViewController guide –
    It is responsible for creating those views and for relinquishing ownership of them at the appropriate times, including during low-memory conditions and when the view controller itself is released.

    So we need to take the ownership to release a view controller.
    Also The UIViewController class provides some automatic handling of low-memory conditions through its didReceiveMemoryWarning method, which releases unneeded memory.

    1. In your Scenario-

    TableView -> on click of cell push next view -> now pop this view to go back to table view(here memory got release) -> in table view again -> on click of cell a new view controller is pushed.

    In this way it handles memory. If in a hierarchy we are pushing some views like –

    VC1 -> VC2 > VC3 -> VC4

    Now in this scenario navigation controller keeps instances of all these view controller, as navigation controller gives us flexibility of moving backward. And as soon as we go back that view controller is removed from stack and memory allocated to that is freed.

    Syntax used –

    Push a view controller –

    [self.navigationController pushViewController:myViewController animated:YES];
[myViewController release];//at the time of push we add this release statement.

    Now when we do a pop, its dealloc method is called and this is removed from the stack.

    [self.navigationController popViewControllerAnimated:YES];//That view is release from navigation stack

    Hope this clears your doubt.
    Checkout this developer page for more details – http://developer.apple.com/library/ios/#featuredarticles/ViewControllerPGforiPhoneOS/ViewLoadingandUnloading/ViewLoadingandUnloading.html

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