MacOS Cocoa, why am i not able to close windows?-CodePudding

i am working in XCode Swift, with Cocoa with Storyboards, and i need to be able to create and close my own windows, programmatically.

to repeat the problem as simply as possible, i start with an empty storyboard project, and change only viewDidLoad in ViewController.swift

override func viewDidLoad() {
    super.viewDidLoad()
    
    let rect = NSRect( x:500, y:500, width:800, height:500 )
    let mask = NSWindow.StyleMask( arrayLiteral: .closable, .miniaturizable, .resizable, .titled )
    let win = NSWindow( contentRect: rect, styleMask: mask, backing: .buffered, defer: false )
    
    win.orderFront( win )
}

the application runs, and puts up two windows. the smaller one is from the storyboard and can be closed without trouble, but when i close the larger window which i created, the application crashes in the appDelegate with

Thread 1: EXC_BAD_ACCESS (code=1, address=0x20)

i assume i am doing something dumb here - what am i missing?

i discovered if i set

win.isReleasedWhenClosed = false

the problem goes away, however i assume the memory is not being released.

i also found that if i append the window handle to an array before closing it, the problem also goes away:

private var broken_windows [NSWindow] = []

public func windowShouldClose( _ sender: NSWindow ) -> Bool {
    
    broken_windows.append( sender )
    return true
}

however this array is somehow completely untouchable, and any attempt to access it's members after the window has been closed will cause the application to crash.

CodePudding user response：

update - the following is not correct, setting isReleasedWhenClosed = false leaves the window open in memory, and is a serious memory leak.

~~it seems that isReleasedWhenClosed = false is the correct answer, after all.~~

~~the following works for me.~~

the following solves the problem of the application crashing, but leaves the window behind in memory, the object is not garbage collected.

class ViewController: NSViewController, NSWindowDelegate {
    
    var win: NSWindow? = nil
    
    public func windowShouldClose( _ sender: NSWindow ) -> Bool {
        if( sender == win ) { win = nil }
        return true
    }
    
    override func viewDidLoad() {

        super.viewDidLoad()
        
        let rect = NSRect( x:500, y:500, width:800, height:500 )
        let mask = NSWindow.StyleMask( arrayLiteral: .closable, .miniaturizable, .resizable, .titled )
        
        win = NSWindow( contentRect: rect, styleMask: mask, backing: .buffered, defer: false )

        win!.delegate = self
        win!.isReleasedWhenClosed = false
        win!.orderFront( win )
    
        DispatchQueue.global(qos: .userInitiated).async {
            sleep(5)
            print( self.win.debugDescription )
        }
    }
}

CodePudding user response：

In your updated code, the window is only retained because you are holding a strong reference to it via self.win. If you use weak var win: NSWindow?, then self.win will be nil after the window is closed. So, setting isReleasedWhenClosed = false does seem to be a valid solution.