UnsafeMutablePointer usage in Swift 3 - uibezierpath

Question

I am using the following extension for UIBezierPath:
extension UIBezierPath {
var elements: [PathElement] {
var pathElements = [PathElement]()
withUnsafeMutablePointer(&pathElements) { elementsPointer in
CGPathApply(CGPath, elementsPointer) { (userInfo, nextElementPointer) in
let nextElement = PathElement(element: nextElementPointer.memory)
let elementsPointer = UnsafeMutablePointer<[PathElement]>(userInfo)
elementsPointer.memory.append(nextElement)
}
}
return pathElements
}
}
This is from the site:
https://oleb.net/blog/2015/06/c-callbacks-in-swift/
However, this breaks with Swift 3 for the following line:
let elementsPointer = UnsafeMutablePointer<[PathElement]>(userInfo)
Following error is displayed:
Cannot invade initializer for type 'UnsafeMutablePointer<[PathElement]>' with an argument list of type '(UnsafeMutableRawPointer?)'
I understand that this is related to the change in Swift 3:UnsafeRawPointerMigration
https://swift.org/migration-guide/se-0107-migrate.html
However, I am not quite sure the best way to port this to Swift 3. Would you be able to provide some help in this regard w/ updated code for the above extension?

Answer 1

I reached out Ole Begemann directly regarding this question. He was very helpful and promptly provided updated code that works with Swift 3. Sharing the same if someone else runs into the same issue as well.
This should work:
extension UIBezierPath {
var elements: [PathElement] {
var pathElements = [PathElement]()
withUnsafeMutablePointer(to: &pathElements) { elementsPointer in
let rawElementsPointer = UnsafeMutableRawPointer(elementsPointer)
cgPath.apply(info: rawElementsPointer) { userInfo, nextElementPointer in
let nextElement = PathElement(element: nextElementPointer.pointee)
let elementsPointer = userInfo?.assumingMemoryBound(to: [PathElement].self)
elementsPointer?.pointee.append(nextElement)
}
}
return pathElements
}
}