UnsafeMutablePointer in swift as replacement for properly sized C Array in Obj-C

Question

How can I interact with functions in swift that used to take sized C arrays?

I read through Interacting with C APIS and still can\'t figure this out.

The doc

Answer 1

Normally you can just pass an array of the required type as an in-out parameter, aka

var coords: [CLLocationCoordinate2D] = []
polyline.getCoordinates(&coords, range: NSMakeRange(0, polyline.pointCount))

but that documentation makes it seem like a bad idea! Luckily, UnsafeMutablePointer provides a static alloc(num: Int) method, so you can call getCoordinates() like this:

var coordsPointer = UnsafeMutablePointer.alloc(polyline.pointCount)
polyline.getCoordinates(coordsPointer, range: NSMakeRange(0, polyline.pointCount))

To get the actual CLLocationCoordinate2D objects out of the mutable pointer, you should be able to just loop through:

var coords: [CLLocationCoordinate2D] = []
for i in 0..

And since you don't want a memory leak, finish up like so:

coordsPointer.dealloc(polyline.pointCount)

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Just remembered Array has a reserveCapacity() instance method, so a much simpler (and probably safer) version of this would be:

var coords: [CLLocationCoordinate2D] = []
coords.reserveCapacity(polyline.pointCount)
polyline.getCoordinates(&coords, range: NSMakeRange(0, polyline.pointCount))