class A { } var a: A = A() func dealloc() { a = A() } let weakClosure = { [weak a] in print(a) // A dealloc() print(a) // nil } weakClosure()class A { } var a: A = A() func dealloc() { a = A() } let weakClosure = { [weak a] in print(a) // A dealloc() print(a) // nil } weakClosure()