Help -- UnityFramework Plugin won't compile (undefined symbols for architecture x86_64)

Apologies if this is a trivial fix, I've lost 2 weeks trying to resolve this.

Any help/suggestions from the community or Unity team would be ****greatly**** appreciated.

Problem:

We are unable to build a Swift project using UnityFramework (uaal) from a workspace for the iOS simulator if I try to use a custom plugin bundled in the Unity Project.

Resulting in:

Why am I even trying to do this?

SwiftUI live previews run on top of the simulator (x86_64), so we are unable to use Uaal without it. I have been able to get uaal working in the simulator and w/ SwiftUI Previews without the custom plugin (a simple bridge/native call proxy), but obviously can't communicate between Unity/Swift without it.

The built Unity-iPhone.xcodeproj w/ the plugin compiles/runs fine independently in the simulator.

When incorporated into a workspace w/ the Swift project, UnityFramework compiles but if I reference the plugin from the Swift project, the Swift build fails w/ the above linker error. If I don't attempt to reference the plugin from my Swift project, it compiles/runs fine in the simulator AND the plugin is loaded (details below). If building to the device, it compiles and I am able to use the plugin as expected.

Setup:

Unity: 2020.2.1f1
Xcode: 12.4
Player settings > Target SDK: Simulator SDK
Player settings > Target minimum iOS Version: 13.0

Plugin (super simplified version):

Unity project:

Spoiler: Assets > Plugins > iOS > Bridge.h

#import <Foundation/Foundation.h>

@interface Bridge : NSObject
@End

Spoiler: Assets > Plugins > iOS > Bridge.m

#import "Bridge.h"

@implementation Bridge
+(void)load
{ NSLog(@"[Bridge loaded]"); }
@End

Xcode settings:

Bridge.h: UnityFramework target, Public
Data: UnityFramework target
UnityFramework Build settings:
Other linker flags: -ObjC
Header search paths: Added "$(SRCROOT)/Libraries/Plugins/iOS/Bridge"
UnityFramework Build phases:
Compile Source: Added Bridge.m
Headers: Bridge.h is public

Checking lipo shows UnityFramework builds correctly for x86_64:

Running Unity-iPhone.xcodeproj independently in the simulator works, and shows the plugin being loaded in the console:

Creating a new workspace w/ Unity-iPhone.xcodeproj and Swift project with:

Spoiler: UnityBridge.swift

//called from a SwiftUI view: UnityBridge.Test()
import Foundation
import UnityFramework

class UnityBridge: UIResponder, UIApplicationDelegate, UnityFrameworkListener {

public static func Test() {

print("Attempting to call bridge");
Bridge.load();​

}​

}

Build fails with the:

If I comment out //Bridge.load(), the build completes successfully and the plugin is loaded when the Swift build runs in the simulator:

Also tried compiling the plugin as a static library or framework:

Tried a few other approaches that seemed more correct:

• Built the plugin as a static library
• Included the built libBridge.a and Bridge.h in Assets/Plugins/iOS/Bridge
• Added a UnityFramework.modulemap to expose the plugin as a submodule as described here.
• Other postprocess build steps to link the library, setup the modulemap, etc.

Build fails with the same x86_64 symbol error.

Really out of ideas here, so if anyone has any suggestions or spots a facepalm mistake it would be greatly appreciated.

Big thanks in advance

 

Are you using the new M1 Chip MacBooks to build? If so, then perhaps you could try setting [excluded architectures to "Arm64"] or something similar.

 

Thanks @teempup_run, appreciate the suggestion.. unfortunately no, am on an intel machine :/

 

Did you try Project Settings -> Player -> Other Settings -> Target SDK : Simulator SDK ?

 

@mspinluca appreciate your comment, yes this is w/ Target SDK : Simulator SDK. Any other ideas appreciated thanks

 

Have you managed to solve or workaround this linking error?

We are having exactly same problems on xcode 12 & Unity 2021.1.12f and so far no luck. :/

We are able to build and run our and Unity projects separately on iOS Simulator but we are not able to link them together. Linker says it can't find UnityFramework to link to (even though we could see it in the output directory - however, it is not built as a *.a or *.so library but it shows as an executable - possible Unity bug?).

 

Hi Chadobado, did you find a solution at the end?

 

Exactly same problem here. I've tried to create custom message bus to communicate with uaal. For unknown reason, XCode strips .mm or .swift implementation for x86_64. arm64 architecture works fine.

We end up using pipeline described in this amazing article:
https://medium.com/mop-developers/c...me-embedded-in-a-swiftui-ios-app-1cefb38ff439

The author managed to do get UnityFramework instance by frameworks bundle:

Code (CSharp):

1.     private func loadUnityFramework() -> UnityFramework? {
2.         let bundlePath: String = Bundle.main.bundlePath + frameworkPath
3.  
4.         let bundle = Bundle(path: bundlePath)
5.         if bundle?.isLoaded == false {
6.             bundle?.load()
7.         }
8.  
9.         let ufw = bundle?.principalClass?.getInstance()
10.         if ufw?.appController() == nil {
11.             let machineHeader = UnsafeMutablePointer<MachHeader>.allocate(capacity: 1)
12.             machineHeader.pointee = _mh_execute_header
13.  
14.             ufw?.setExecuteHeader(machineHeader)
15.         }
16.         return ufw
17.     }

If you try to call

UnityFramework.getInstance()

, the x86_64 linker will fail. But

principalClass

works great both on simulator and real device.

 

After a lot of research, I found solution for your problem.

I don't know why, but

Bridge.Load()

won't work on a simulator. I suggested before to use principal class, but in an article above I found much better solution

You can use

NSClassFromString

to load your custom class dynamically and avoid Linker issue. It works similar to reflection in C#. The working code should be something like this:

Code (CSharp):

1. NSClassFromString("Bridge").Load()