// Copyright (c) 2013 Cocoanetics. All rights reserved.
Useful defines for building code the compiles with zeroing weak references if the deployment target allows it. This is possible from minimum supported iOS 5.0 and OS X 10.7 and above. Note that on OS X 10.7 some AppKit classes do not support having a weak ref, e.g. NSWindowController or NSViewController.
// zeroing weak refs are supported for ivars and properties
#define DT_WEAK_VARIABLE __weak
#define DT_WEAK_PROPERTY weak
/// zeroing weak refs not supported, fall back to unsafe unretained and assigning
#define DT_WEAK_VARIABLE __unsafe_unretained
#define DT_WEAK_PROPERTY assign
// define something, as this header might be included in a non-ARC project for using compiled code from an ARC static lib