Does not have a member named 'subscript' - swift

Question

I'm building something and it all worked fine until Swift 1.2 came out. I made some changes but still have one line of code that is playing nice. I don't understand why this is breaking:
let swiftArray = positionDictionary.objectForKey["positions"] as? [AnyObject]
it gives me an error:
'(AnyObject) -> AnyObject?' does not have a member named 'subscript'
I also tried using this:
let swiftArray = positionDictionary.objectForKey?["positions"] as? [AnyObject]
but then I get an error saying:
Operand of postfix '?' should have an optional type; type is '(AnyObject) -> AnyObject?'
I'm really confused...can anyone help?
func addOrbsToForeground() {
let orbPlistPath = NSBundle.mainBundle().pathForResource("orbs", ofType: "plist")
let orbDataDictionary : NSDictionary? = NSDictionary(contentsOfFile: orbPlistPath!)
if let positionDictionary = orbDataDictionary {
let swiftArray = positionDictionary.objectForKey["positions"] as? [AnyObject]
let downcastedArray = swiftArray as? [NSArray]
for position in downcastedArray {
let orbNode = Orb(textureAtlas: textureAtlas)
let x = position.objectForKey("x") as CGFloat
let y = position.objectForKey("y") as CGFloat
orbNode.position = CGPointMake(x,y)
foregroundNode!.addChild(orbNode)
}
}

Answer 1

positionDictionary is an NSDictionary. You can use it just like a Swift dictionary - you don't need to use objectForKey.
You should just use if let and optional casting to get the value you want, which I think is an array of NSDictionary since you're using objectForKey again later:
if let downcastedArray = positionDictionary["positions"] as? [NSDictionary] {
for position in downcastedArray {
let orbNode = Orb(textureAtlas: textureAtlas)
let x = position["x"] as CGFloat
let y = position["y"] as CGFloat
orbNode.position = CGPointMake(x,y)
foregroundNode!.addChild(orbNode)
}
}
As a side note, CGPointMake is not stylistically preferred in Swift. Instead, consider using the CGPoint initializer:
orbNode.position = CGPoint(x: x, y: y)