Hands-On Design Patterns with Swift

Dangling pointers

Dangling pointers are the opposite of over-retained objects. You can encounter dangling pointers when trying to access a deallocated object. This is best illustrated by the following example:

- (void) doSomething {    MyObject *myObject = [[MyObject alloc] init]; // retainCount is +1    [myObject release]; // retain count is 0; object is deallocated    // More things happening in this method    [myObject myMethod];}

This may not cause a crash all of the time, as myObject could be properly set to nil. When it crashes, you'll face the dreaded NSInvalidArgumentException, which, upon first glance, doesn't make much sense:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[<insert a type here> myMethod]: ...