how to use AXUIElementCopyAttributeValue from Swift? - objective-c

Question

I am trying to use AXUIElementCopyAttributeValue from Swift. My best stab currently looks like this:
private func mainWindow() -> Optional<AXUIElementRef> {
let appRef = AXUIElementCreateApplication(self.pid())
var ptr: Unmanaged<AXUIElementRef>? = nil
var frontWindow: AXUIElementRef? = nil
let err = AXUIElementCopyAttributeValue(appRef, kAXMainWindowAttribute, &ptr)
if err == AXError(kAXErrorSuccess) {
frontWindow = ptr!.takeRetainedValue()
}
return frontWindow
}
Unfortunately kAXMainWindowAttribute is not in scope. This works in ObjC of course, but I can't figure out where the value is hiding when accessed from Swift. This isn't the first time I've had this problem, either, although previously I've been able to stumble around a bit and find it.
Also, I'd be happy to receive any stylistic suggestions here. I'm not convinced I'm doing this in the most natural way for Swift.

Answer 1

It is an old question but I still drop it here in case someone else searches for it:
let appRef = AXUIElementCreateApplication(pid)
var value: AnyObject?
AXUIElementCopyAttributeValue(appRef, kAXMainWindowAttribute as CFString, &value)
also, I assume you get the "Swift dynamic cast failed" error message because you try to cast from AXUIElement to AnyObject. You can cast it like so:
print(value as! AXUIElement)

Answer 2

This is not an answer yet, but perhaps might help someone get me an answer... I changed the code to this, in order to make forward progress:
func mainWindow() -> WBWindow? {
var result: WBWindow? = nil
var ptr: Unmanaged<AnyObject>?
let kAXMainWindow: CFString! = "AXMainWindow" as NSString
let appRef: AXUIElement! = AXUIElementCreateApplication(self.pid()).takeRetainedValue()
let err = AXUIElementCopyAttributeValue(appRef, kAXMainWindow, &ptr)
if err == AXError(kAXErrorSuccess) {
let val: AnyObject? = ptr?.takeRetainedValue()
if val != nil {
let value: AnyObject = val!
let description = CFCopyTypeIDDescription(CFGetTypeID(value))
println("type = \(description)")
}
else {
NSLog("got nil result")
}
// result = WBWindow(element: ptr?.takeRetainedValue() as? AXUIElement)
}
return result
}
This now builds -- yay! But, when running, the commented out line drops me into a stack:
0x1001b57ea: leaq 0x3f1a1(%rip), %rax ; "Swift dynamic cast failed"
I added the debugging code above and that produces:
type = AXUIElement
Sooooo. It's an AXUIElement that won't cast to one? Clearly I'm missing something obvious...