How to access `enum` values and provide a `completionHandler`? (Request iOS local notification permission)

[loftafi]

I have been exploring if I can use zig-objc to replace my clunky swift side build. I first checked to see if there was sample code that might demonstrate the intent for how we would access enum values (to create an NSUInteger) and how to provide a completionHandler

    // UNUserNotificationCenter *un = [UNUserNotificationCenter currentNotificationCenter];
    const un = objc.getClass("UNUserNotificationCenter").?;
    const cnc = un.msgSend(objc.Object, "currentNotificationCenter", .{});

    // https://developer.apple.com/documentation/usernotifications/unauthorizationoptions
    // UNAuthorizationOptions options = UNAuthorizationOptionAlert +
    //     UNAuthorizationOptionSound +
    //     UNAuthorizationOptionBadge;
    const options = objc.enum??.UNAuthorizationOptions??? //enum UNAuthorizationOptions : NSUInteger;

    //[un requestAuthorizationWithOptions:(UNAuthorizationOptions) options 
    //    completionHandler:(void (^)(BOOL granted, NSError *error)) completionHandler];
    cnc.msgSend(objc.Object, "requestAuthorizationWithOptions", .{
        options,
        completionHandler, // Can this be just a function?
    });
}

Any input would be greatly appreciated.

PS: By way of feedback, I wonder if we could get an /examples folder for zig-objc to demonstrate some more advanced basic patterns like this. Thanks for your work on this cool zig project.

[loftafi]

On part 1, how to use enums, I discovered this example from ghostty, which appears to just redefine the enum in zig. So I'll do this.

https://github.com/marler8997/ghostty/blob/main/src/os/macos.zig

Not sure it's the nicest looking code. Maybe there is a better way:

const UNAuthorizationOptions = enum(c_uint) {
    UNAuthorizationOptionBadge = (1 << 0),
    UNAuthorizationOptionSound = (1 << 1),
    UNAuthorizationOptionAlert = (1 << 2),
    UNAuthorizationOptionCarPlay = (1 << 3),
};

const options = @intFromEnum(UNAuthorizationOptions.UNAuthorizationOptionAlert) +
        @intFromEnum(UNAuthorizationOptions.UNAuthorizationOptionBadge) +
        @intFromEnum(UNAuthorizationOptions.UNAuthorizationOptionSound);

On part 2, now trying to work out how to define a completionHandler. There is some example Block code, but I don't know how to use it, ie this compiles, but of course doesn't work. Not sure what I need to put where:

const Response = objc.Block(struct { granted: bool, err: i32 }, .{}, void);
var completionHandler = Response.init(.{ .granted = false, .err = 3 }, (struct {
        fn addFn(_: *const Response.Context) callconv(.c) void {
            std.log.info("approved: {any}", .{true});
            return;
        }
}).addFn);

//[un requestAuthorizationWithOptions:(UNAuthorizationOptions) options
//    completionHandler:(void (^)(BOOL granted, NSError *error)) completionHandler];
const result = cnc.msgSend(objc.Object, "requestAuthorizationWithOptions:completionHandler:", .{
        options,
        &completionHandler, // Can this be just a function?
    });
std.log.info("response={any}", .{result});
// What is the appropriate way to wait/pause for the callback?

[loftafi]

I guess the main thing, if I got everything else correct, is how do I put an NSError in objc.Block(struct { granted: bool, err: i32 }, .{} void)

https://github.com/loftafi/obj-c-testing

If I try using err: *anyopaque I can run the binary, but it fails with:

19:27msg main $ zig build run
info: info=true
info: Found UNUserNotificationCenter.
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'bundleProxyForCurrentProcess is nil: mainBundle.bundleURL file:///Volumes/user/msg/zig-out/bin/'
*** First throw call stack:
(
        0   CoreFoundation                      0x000000018f226bf0 __exceptionPreprocess + 176
        1   libobjc.A.dylib                     0x000000018ecb291c objc_exception_throw + 88
        2   Foundation                          0x0000000190ab41a0 -[NSCalendarDate initWithCoder:] + 0
        3   UserNotifications                   0x000000019ece18ac __53+[UNUserNotificationCenter currentNotificationCenter]_block_invoke.cold.2 + 104
        4   UserNotifications                   0x000000019ecad49c __53+[UNUserNotificationCenter currentNotificationCenter]_block_invoke + 472
        5   libdispatch.dylib                   0x000000018ef5a4b0 _dispatch_client_callout + 16
        6   libdispatch.dylib                   0x000000018ef43630 _dispatch_once_callout + 32
        7   UserNotifications                   0x000000019ecad2c0 +[UNUserNotificationCenter currentNotificationCenter] + 176
        8   msg                                 0x0000000104801f48 main + 4936
        9   dyld                                0x000000018ed3fda4 start + 6992
)
libc++abi: terminating due to uncaught exception of type NSException
run exe msg failure
error: process terminated with signal ABRT

It feels so close, yet so far.

[loftafi]

It turns out that this error might be related to a need to run this code inside an app bundle. So perhaps this will work. ...

https://developer.apple.com/forums/thread/679326