Question

Here is my scenario:

Main VC : Scroll View : [Multiple] MyPage : [Multiple] ObjectView : [Multple] UIButton

I have my main view controller containing a UIScrollView. The Scroll view is supposed to load multiple “MyPage” Views with pagingEnabled. I use the IB to create the “MyPage” interface (MyPage.xib) and view controller files (MyPage.h &.m). MyPage.xib file owner is set to MyPage. This “MyPage” will again load multiple ObjectView which again I created through IB with (ObjectView.xib, ObjectView.h, ObjectView.m)

Both of the MyPage & ObjectView class are subclass of UIViewController which hold some of my data properties.

The ObjectView class have several buttons and I have those button Touch Up actions connected by control drag the button to my ObjectView.h.

In my Main VC’s viewDidLoad method, I have a loop that will add all the pages:

- (void)viewDidLoad {
  ...
  for (int i=0; i<numPages; i=i+1) {
    MyPage *spg =[[MyPage alloc]i init];
    ...definition of spg properties...
    [spg loadPage:i+1];
    [scrollView addSubview:spg.view];
  }
}

In the MyPage loadPage method, I have a loop that will add all the ObjectView

- (void) loadPage:(int) x {
  ...
  for (int i=0; i<numObjects; i++) {
    ObjectView *objvc = [[ObjectView alloc] init];
    ... defining objvc frame coordinates && other properties ...
    [self.view addSubview:objvc.view];
  }
}

In ObjectView, there are several buttons and I connect those buttons to TouchUp actions in IB through Ctrl-Drag the buttons to my ObjectView.h.

The App is successfully build, the scroll view did load, all pages and all objects are displayed nicely. However, when I touch the buttons the following run-time error appears:

Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason:

-[TitleLayouer touchBtnOnline:]: unrecognized selector sent to instance 0x17f810′

I try to put break point on my first statement in my button action method, however that break point cannot even be reached.

Hope someone can help me with this issue.

Answer 1

I find out the problem and solution. The problem is due to ARC releasing the ObjectView and MyPage object when they are outside their scope (the loop?), so in run-time it cannot reference to the View Controller objects in memory anymore.

The solution is to have a NSMutableArray property in the View Controller (and remember to alloc it with init, I once forgot about it and it causes another memory error…). Inside the loop, add the view controller objects (ObjectView/MyPage) to the array so these objects will be retained in the memory.