Xcode 8 beta 6: main.swift won't compile

Question

We have a custom UIApplication object, so our main.swift was

import Foundation
import UIKit

UIApplicationMain(Process.argc, Process.unsafeArgv, NSStringFrom         


        

Answer 1

I write it this way:

UIApplicationMain(
    CommandLine.argc,
    UnsafeMutableRawPointer(CommandLine.unsafeArgv)
        .bindMemory(
            to: UnsafeMutablePointer.self,
            capacity: Int(CommandLine.argc)),
    nil,
    NSStringFromClass(AppDelegate.self)
)

To change the UIApplication class, substitute NSStringFromClass(MobileUIApplication.self) for nil in that formulation.

However, if your only purpose here is to substitute a UIApplication subclass as the shared application instance, there's an easier way: in the Info.plist, add the "Principal class" key and set its value to the string name of your UIApplication subclass, and mark your declaration of that subclass with an @objc(...) attribute giving it the same Objective-C name.

EDIT This problem is now solved in Swift 4.2. CommandLine.unsafeArgv now has the correct signature, and one can call UIApplicationMain easily:

UIApplicationMain(
    CommandLine.argc, CommandLine.unsafeArgv, 
    nil, NSStringFromClass(AppDelegate.self)
)