SLN SLN - 9 months ago 148
Swift Question

Xcode8 Beta EXC_BAD_ACCESS Error appears when creates weak references

The following code is copied from the Weak References section of the Official document

class Person {
let name: String
init(name: String) { = name }
var apartment: Apartment?
deinit { print("\(name) is being deinitialized") }

class Apartment {
let unit: String
init(unit: String) { self.unit = unit }
weak var tenant: Person?
deinit { print("Apartment \(unit) is being deinitialized") }

var john: Person?
var unit4A: Apartment?

john = Person(name: "John Appleseed")
unit4A = Apartment(unit: "4A")

john!.apartment = unit4A
unit4A!.tenant = john //Error!

It basically described the strong and weak reference relationship between a
type instance and an
type instance (Please see the figure bellow)

enter image description here

However, when I run the code, I got an error.

Question: How can I fix it?

enter image description here

In reply of Mr. Alessandro Orrù, (I copy and pasted it again and it still gives me error)

enter image description here


This now works correctly - the bug has been fixed in XCode 8 GM Seed.

Original Answer:

It's a bug in playgrounds in or XCode8 beta 3. I copied your code, tried the Apple example, and tried reducing it to the minimum:

class A { var b:B? }

class B { weak var a:A? }

let b = B()
let a = A()


All work as expected with XCode 7.3.1 and Swift 2.2. All fail with XCode 8 beta 3 and Swift 3. The error is:

error: Playground execution aborted: error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=EXC_I386_GPFLT).

It's in playgrounds only - it's fine in an app. (I tried a Mac OS command line program)