Why can the keyword “weak” only be applied to class and class-bound protocol types

Question

When I\'m declaring variables as weak in Swift, I sometimes get the error message from Xcode:

\'weak\' may only be applied to class and

Answer 1

I tried to capture String and Array-typed properties for a closure. I got these errors:

'weak' may only be applied to class and class-bound protocol types, not '[String]'

'weak' may only be applied to class and class-bound protocol types, not 'String'

I played a while in the playground, and it turned out, capturing self is enough for these types.