Weak and strong property setter attributes in Objective-C

Question

What is the difference between weak and strong property setter attributes in Objective-C?

@property(retain, [weak/strong]) __attribute__((NSObject)) CFDictio         


        

Answer 1

To call out the parts of the docs referenced by Robert that answer your last two questions explicitly:

// The following declaration is similar to "@property(assign) MyClass *myObject;"
// except that if the MyClass instance is deallocated,
// the property value is set to nil instead of remaining as a dangling pointer.
@property(weak) MyClass *myObject;

This is referred to as a zeroing weak reference. You can create weak references that are not zeroing weak references using __unsafe_unretained, but as the name implies, this is generally not recommended.

Also in the docs:

Weak references are not supported in Mac OS X v10.6 and iOS 4.