Search code examples
c#iosxamarinmaui

MAUI error: retain (or strong) attribute on property 'window' does not match property inherited from UIApplicationDelegate

I have a dotnet 8 MAUI IOS app that I am attempting to build and run on a physical IOS device connected to my Mac via a USB. When I run the debugger I am getting the following error:

/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error : clang exited with code 1: [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error : In file included from /Users/user/Projects/cds-tims-mobile-client/obj/Debug/net8.0-ios/ios-arm64/linker-cache/registrar.mm:3: [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error : /Users/user/Projects/cds-tims-mobile-client/obj/Debug/net8.0-ios/ios-arm64/linker-cache/registrar.h:257:43: warning: 'retain (or strong)' attribute on property 'window' does not match the property inherited from 'UIApplicationDelegate' [-Wproperty-attribute-mismatch] [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error :   257 |         @property (nonatomic, assign) UIWindow * window; [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error :       |                                                  ^ [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error : /Users/user/Projects/cds-tims-mobile-client/obj/Debug/net8.0-ios/ios-arm64/linker-cache/registrar.h:289:43: warning: 'retain (or strong)' attribute on property 'window' does not match the property inherited from 'UIApplicationDelegate' [-Wproperty-attribute-mismatch] [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error :   289 |         @property (nonatomic, assign) UIWindow * window; [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error :       |                                                  ^ [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8303/targets/Xamarin.Shared.Sdk.targets(1455,3): error : /Users/user/Projects/cds-tims-mobile-client/obj/Debug/net8.0-ios/ios-arm64/linker-cache/regist [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]
    9 Warning(s)
    1 Error(s)

The relevant part here I think is

warning: 'retain (or strong)' attribute on property 'window' does not match the property inherited from 'UIApplicationDelegate' [-Wproperty-attribute-mismatch] [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]

I googled around a bit and have tried a few things. I changed my AppDelegate file:

using Foundation;
using UIKit; // Add this to resolve UIWindow

namespace TIMS;

[Register("AppDelegate")]
public class AppDelegate : MauiUIApplicationDelegate
{
    [Export("window")]
    public override UIWindow? Window { get; set; }

    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
}

Adding this part:

[Export("window")]
public override UIWindow? Window { get; set; }

That didn't change anything. Someone on Github also recommended setting MtouchLink in the csproj file to sdkOnly:

<MtouchLink>SdkOnly</MtouchLink>

But this also did not help. I have also made sure to delete the obj and bin folder and try again but that still did not help.

Any assistance would be greatly appreciated.

EDIT:

Upon further testing I am not sure if I was on the right track whatsoever. I have altered my app delegate class to look like this:

using Foundation;

namespace TIMS;

[Register("AppDelegate")]
public class AppDelegate : MauiUIApplicationDelegate
{
    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
}

and I still get the same error.

I have research this a bit and my problem seems to be more specifically this:

The attribute on my window property (nonatomic, assign) does not match what UIApplicationDelegate expects (retain or strong). The line @property (nonatomic, assign) UIWindow * window; is in an automatically generated Objective-C header file (registrar.h) that is generated during the build process in a Xamarin or .NET MAUI iOS project. It is part of the Objective-C interop code generated by the Xamarin.iOS or .NET MAUI toolchain, which is responsible for marshaling between C# and Objective-C during the build.

So I need to find a way to get my AppDelegate to generate the line @property (nonatomic, strong) UIWindow * window; instead of @property (nonatomic, assign) UIWindow * window;.

Solution

  • warning: 'retain (or strong)' attribute on property 'window' does not match the property inherited from 'UIApplicationDelegate' [-Wproperty-attribute-mismatch] [/Users/user/Projects/cds-tims-mobile-client/TIMS.csproj]

    but the app never actual built or ran on my phone. Every subsequent time I have tried running it on the phone I get the exact same error as my above app

    You can report your situation on this issue: warning "retain (or strong)' attribute on property ... #10722, or create a new issue for it on MAUI GitHub issue. Let our developers know and deal with it.