Need assistance regarding UIViewController life cycle

Question

In a chat based app I have UITableView which display all friends name, on didSelectRowAtIndex I am pushing to chatViewController using navigationcontroller push method.

I have two confusion:

1> When I push chatViewController I do it like this

 chatViewController *cVc = [[chatViewController alloc]initWithFriendName:@"the name" andId:@"the id"];

There can be 10 or 50 or 100 friends, is it correct to call alloc init for every friend?

2> When user tap back button to go back to friends list, what happen to chatViewController's current instance when it will be destroyed to free memory?

score 2 · Accepted Answer · answered May 02 '13 at 07:50

2

Yes, if this instance of chatViewController is for this specific friend.
The back button does a implicit popViewControllerAnimated: which pops the chatViewController from the navigation stack and destroys it (unless you have saved a strong reference to that view controller somewhere).

So there will be only one instance of chatViewController at a time (created in didSelectRowAtIndex and destroyed by popViewControllerAnimated: when the user goes back to the table view).

answered May 02 '13 at 07:50

Martin R

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thanks for replying, my mistake cVc is not global, it is for specific friend. – S.J May 02 '13 at 08:10
@S.J: For my answer I had assumed that vVC is a local instance created in `didSelectRowAtIndex`. – Martin R May 02 '13 at 08:14
please also view this question http://stackoverflow.com/questions/16333731/need-assistance-regarding-uiviewcontroller – S.J May 02 '13 at 08:45
I would like to invite you to answer this question http://stackoverflow.com/questions/17657719/please-clear-some-confusions-regarding-uiviewcontroller – S.J Jul 16 '13 at 05:26

score 0 · Answer 2 · answered May 02 '13 at 07:54

Since you are creating the global instance of chatViewController and allocting it each and everytime the didSelectRowAtIndexpath: method is called , this is the wrong way as it will un-necessarily utilising the memory and thus degrades the app performance . You must create the local instance in the method didSelectRowAtIndexpath:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
     ChatViewController *_cvc = [[ChatViewController alloc] initWithFriendName:@"the name" andId:@"the id"];

     [self.navigationController pushViewController:_cvc animated:YES];
}

Answer for your second question is whenever the user presses the back button , the instance is destroyed

In your answer call will be "allocating it each and every time" as well — art-divin, May 02 '13 at 07:56
Yes, call will be allocating the instances everytime but the lifetime of the instances will be weak and would get automatically destroyed as soon as they are no longer in uses — Gaurav Rastogi, May 02 '13 at 08:12

Need assistance regarding UIViewController life cycle

2 Answers2