Thanks! That works just as it should. It's all compiling and unit tests
are passing, so I can move on now.
Mike Ferenduros <mailto:mike.ferendu...@gmail.com>
30 September 2016 at 14:14
The way to do this is via Unmanaged:
let raw = Unmanaged.passUnretained(expat).toOpaque()
gets you an UnsafeMutableRawPointer you can pass into C functions. You
can turn this back into an ExpatSwift with
let expat =
Unmanaged<ExpatSwift>.fromOpaque(raw).takeUnretainedValue()
There are also retained variants that will add or remove a reference
to the object in question.
Basically, if you know that the pointer won't outlive the thing it
references, you want the unretained variants. This is usually what you
want when you're wrapping C APIs with callbacks, especially if
callbacks happen synchronously.
On the other hand, if the pointer lives independently of the Whatever
then you may want to
- create the pointer with passRetained(), which will keep the object
it points to alive
- access the object with take*Un*retainedValue() (so you don't
prematurely release your reference to it), and
- call release() on it when you're done with it.
If you forget the 3rd step then you're leaking memory, and if you
miscalculate and do it twice then you crash.
Or if you're just passing a pointer from A to B one time, you can use
passRetained() + takeRetainedValue().
--
John Brownie
In Finland on furlough from SIL Papua New Guinea
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