> On Mar 13, 2017, at 10:56 AM, rintaro ishizaki via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
>
> final class First {
> let item: First
> init(item: First) {
> self.item = item
> }
> }
>
> extension First {
> convenience init() {
> self.init(item: self)
> }
> }
>
> let a = First()
>
> I'm actually a bit surprised that this compiles.
> This should be diagnosed as: "error: 'self' used before self.init call" I
> think.
Interestingly enough, this code:
final class First {
let item: First
// let int: Int
let string: String
init(item: First) {
self.item = item
// self.int = item.int
self.string = item.string
}
}
extension First {
convenience init() {
self.init(item: self)
}
}
let a = First()
//print("a.int:")
//print(a.int)
print("a.string:")
print(a.string)
print("done”)
Outputs
a.string:
fatal error: unsafelyUnwrapped of nil optional
(followed by a trace and lldb prompt)
But if I switch which stored properties are commented out (and printed), it
usually outputs:
a.int:
562949953421312
done
Program ended with exit code: 0
or
a.int:
0
done
Program ended with exit code: 0
with the one exception being when `a.int`’s value started with a 7 instead of a
5 (but I didn’t think to copy/paste it). That’s not the interesting part,
though. If both properties are uncommented and printed, it seems to always
output:
a.int:
0
a.string:
done
Program ended with exit code: 0
(note that `a.string` seems be equal to “” now)
Anyway, I’d assume this is just a demonstration of the dangers of accessing
uninitialized memory, but what I don’t know is why having two properties seems
to remove the randomness in one’s value and stops the crashing when accessing
the other's.
- Dave Sweeris_______________________________________________
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