Open Radar

 
Swift defines a mechanism to avoid retain cycle in blocks (that are affected to property of self)

var myClosure = {
    [weak obj] in
    println(obj?.description)
}

This is not clear whether self is constant within the block or not. In Obj-C, 2 possible approach are possible:

Approach A:
__weak id obj;
^{
	NSLog(obj);
	NSLog(obj);
}

OR

Approach B:
__weak id obj;
^{
	__strong id sobj = obj;
	NSLog(sobj);
	NSLog(sobj);
}

The first approach makes it so that obj can become nil at any point within the block, while approach B makes it either nil or not nil but non-changing  within the block.

In Swift, it's not clear whether Approach A or B applies when using the [weak obj] pattern.