I’ve run into a problem with an iPhone core data application that I’m working on. I have a table that lists objects. If I select one of those objects, I go to a new ViewController that shows the detail for the object.
In the detail view, I have a back button that takes me back to the main list view.
I can select any number of rows and it will show me the detailed view for each. However, if I attempt to select a row that I’ve already selected, it crashes with
Program received signal:
“EXC_BAD_ACCESS”.
I’ve added some breakpoints and tried to track this down, and found the following in my tableView cellForRowAtIndexPath method…
The first time through for each object when I do a
MyEntity *thingamy = [fetchedResultsController objectAtIndexPath:indexPath]
thingamy is valid and set to a valid thingamy. In gdb, I can set a breakpoint at this point and do a
po thingamy
and I get the expected output.
However, the second time I select a specific row (e.g. select row 0, go back, select row 0 again), thingamy is not setup correctly.
I can view any number of other rows, but as soon as I attempt to select a row I have already viewed the detail for this occurs.
If I have the breakpoint in place and I try to do a po thingamy after it is set, I get the following:
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x00000020
0x92ca3ed7 in objc_msgSend ()
Any idea why fetchedResultsController returns a valid object the first call, but not the second?
UPDATE
After a few days now, I’m positive that it is not an issue with the fetchedResultsController being dealloc’d. I’ve enabled NSZombieEnabled mode, and there is nothing there.
Additionally, I can get other objects from the fetchedREsultsController, just not the one I have already accessed.
For example, I can get
[fetchedResultsController objectAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] and display that in my next view.
When I hit back and get back to my parent view, I can then get the object at indexPathForRow:0 inSection:1 and display that.
Coming back to the beginning again, I try to get indexPathForRow:0 inSection:0 and it crashes with EXC_BAD_ACCESS.
In a table with 100 rows, I can get every single row once, but any attempt to get the same row twice crashes, even if those attempts are one after another.
I finally found the answer to this!
In my dealloc section, I was deallocing a number of variables instead of releasing them. Now that I’ve changed these to release, everything is working as expected.