UICollectionView crash on scroll

Question

I tried to create a UICollectionView using the Flow Layout. The cells are simply text labels for the time being. The first screen of cells is displayed just fine, but when I try to scroll, the simulator crashes. The debugger shows the following messages:

(lldb) thread backtrace
  * thread #1: tid = 0x39235a, 0x008440b2 libobjc.A.dylib`objc_msgSend + 14, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xa000000c)
  * frame #0: 0x008440b2 libobjc.A.dylib`objc_msgSend + 14
    frame #1: 0x01ab9b30 UIKit`-[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:] + 257
    frame #2: 0x01abb775 UIKit`-[UICollectionView _updateVisibleCellsNow:] + 4730
    frame #3: 0x01abf65f UIKit`-[UICollectionView layoutSubviews] + 265
    frame #4: 0x014e2964 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
    frame #5: 0x0084682b libobjc.A.dylib`-[NSObject performSelector:withObject:] + 70
    frame #6: 0x0280e45a QuartzCore`-[CALayer layoutSublayers] + 148
    frame #7: 0x02802244 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 380
    frame #8: 0x028020b0 QuartzCore`CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 26
    frame #9: 0x027687fa QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 294
    frame #10: 0x02769b85 QuartzCore`CA::Transaction::commit() + 393
    frame #11: 0x0276a258 QuartzCore`CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 92
    frame #12: 0x02bd936e CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
    frame #13: 0x02bd92bf CoreFoundation`__CFRunLoopDoObservers + 399
    frame #14: 0x02bb7254 CoreFoundation`__CFRunLoopRun + 1076
    frame #15: 0x02bb69d3 CoreFoundation`CFRunLoopRunSpecific + 467
    frame #16: 0x02bb67eb CoreFoundation`CFRunLoopRunInMode + 123
    frame #17: 0x05f5b5ee GraphicsServices`GSEventRunModal + 192
    frame #18: 0x05f5b42b GraphicsServices`GSEventRun + 104
    frame #19: 0x01473f9b UIKit`UIApplicationMain + 1225
    frame #20: 0x0002423c 8actions`main(argc=1, argv=0xbfffe610) + 156 at main.mm:15

I am using the latest version of rubymotion and the IOS Simulator set to iPhone 4 Inch with IOS 7.1. The code I am using can be found here:

https://gist.github.com/jhmegorei/42c15038a34971ac5e8e

Note: I did not want to use a CollectionViewController, as I require the collection View to be just another view element that can be added to a normal UIView.

I would be glad if there is anyone who could help me investigate the root cause of this crash :)

Answer 1

There is no "MemoListViewDelegate.rb" in the gist. Did you mean "MemoListDataSource.rb" ?

Also, I assume you mean you changed

  list_view.dataSource       = MemoListDatasource.new

to

  list_view.dataSource       = self

as well as moving the data source methods in there.

Did you make any other changes to get it to work?