How can you implement the NSDocument method -canCloseDocumentWithDelegate:shouldCloseSelector:contextInfo: in Swift?

Question

In my application, a NSDocument subclass mission-critical hardware – users really don’t want to close a document by accident! So, I’ve implemented canClos

Answer 1

You can solve this with some low level runtime functions:

override func canCloseDocumentWithDelegate(delegate: AnyObject, shouldCloseSelector: Selector, contextInfo: UnsafeMutablePointer) {

    let allowed = true // ...or false. Add your logic here.

    let Class: AnyClass = object_getClass(delegate)
    let method = class_getMethodImplementation(Class, shouldCloseSelector)

    typealias signature = @convention(c) (AnyObject, Selector, AnyObject, Bool, UnsafeMutablePointer) -> Void
    let function = unsafeBitCast(method, signature.self)

    function(delegate, shouldCloseSelector, self, allowed, contextInfo)
}

If you need to move this behaviour to another method (eg. after a sheet gets confirmation from the user), simply store the delegate and shouldCloseSelector in properties so you can access them later.