Hello,
I was testing my application and suddenly it had EXC_BAD_ACCESS. Now this has become a semi-regular thing, happening on some builds and not others. It also spits out lots of errors in the debugger such as objc_msgSend_vtable5 What could cause such a weird issue like this?
Looks like it was my fault. To fix it all I needed to do was call retain.
I've recently had just this same error. The short version: it occurred because I had an object that had a delegate that had been released. Make sure you have control over the life cycle of any delegates you assign, be it via Interface Builder or otherwise.
The long version: the error occurs when the Objective-C runtime tries to send a message to an object that's been ultimately released and deallocated. This is different to sending a message to a nil object (a perfectly valid Objective-C operation). In these cases, the runtime knows that the object is nil and responds accordingly. Rather, in this case, Objective-C thinks it has a real, valid object to communicate with and sends a message to an address that contains no object.
In my case, I had an object of type NSTextView which was connected up to a delegate by Interface Builder. When a view or view controller is constructed with a NIB/XIB file, Cocoa hooks up all the child views as instructed, including hooking up any delegates that you might have.
My error was that I had created a subclass of NSView, made it an NSTextViewDelegate and then told Interface Builder to hook up a child NSTextView to that parent view. However, during the various operations I was conducting on the owning NSViewController, I had told Cocoa to remove the NSView from the view hierarchy and reinsert it later.
AppKit specifically tells you not to retain any IBOutlets you might have in your classes, but rather to keep track of these by simple assignment. This is because AppKit handles the memory management of these for you. Little did I know that by asking the view to leave the view hierarchy for a while, I had trigged AppKit to clean up that NSView. Since only AppKit had any retains on the view object itself, [pfft], off it went into the ether. Deallocated.
Since I had no direct control over the NSTextView's delegate, the NSTextView now pointed to a delegate that had been released, even though it had a valid parent view. The next time it tried to send a message to its delegate, the Objective-C runtime fell over.
So, make sure that the delegate is one that you own, or at least know will never get released at an inopportune moment.