Swift get value from UnsafeMutablePointer using UnsafePointer

Question

I am trying to pass contextInfo of typeUnsafeMutablePointer to UISaveVideoAtPathToSavedPhotosAlbum and use it in the callback

Answer 1

As discussed in OP comments, testStr has already been freed.

Is there any way to force the retaining of a variable that has been created in a function? Then release it later?

It's not impossible, but I don't know this is the best way to do that.

Anyway, try this with Playground or OS X "Command Line Tool" template:

import Foundation

func foo() {
    var str:NSString = "Hello World"
    let ptr = UnsafePointer(Unmanaged.passRetained(str).toOpaque())
    bar(ptr)
}

func bar(v:UnsafePointer) {
    let at = dispatch_time(
        DISPATCH_TIME_NOW,
        Int64(2.0 * Double(NSEC_PER_SEC))
    )
    dispatch_after(at, dispatch_get_main_queue()) {
        baz(v)
    }
}

func baz(v:UnsafePointer) {
    println("notified")
    let str = Unmanaged.fromOpaque(COpaquePointer(v)).takeRetainedValue()
    println("info: \(str)")
}


foo()

println("started")

dispatch_main()

• Unmanaged.passRetained(str) increments the retain count.
• Unmanaged.fromOpaque(...).takeRetainedValue() decrements it, and extract the object.

I think, using pure Swift String is impossible. because String is struct and is allocated in stack memory. Maybe the buffer of it is allocated in heap, but we cannot access it directly.