Display file chooser dialog

Question

How do I show a file chooser dialog on Mac OS X? The language is Objective C.

Answer 1

Those who are looking for Swift version

let panel                     = NSOpenPanel()
panel.canChooseDirectories    = false
panel.canChooseFiles          = true
panel.allowsMultipleSelection = false
panel.allowedFileTypes        = ["txt"]
let clicked                   = panel.runModal()

if clicked == NSApplication.ModalResponse.OK {
    print("URLS => \(panel.urls)")
}