Passing data from SwiftUI to Unity

Unity Engine
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1

I’m trying to set up some SwiftUI sliders to modify Unity properties. I feel like I have a good handle on sending data from Unity to SwiftUI (@DanMillerU3D 's linkedIn post really helped) but I’m stuck on how to get values back from SwiftUI to Unity. I think I’m fine on the C# side, but I’m not sure how to create my own delegate/callback like the SwiftUISamplePlugin CallbackDelegateType/CallCSharpCallback that receives types of data other that strings.

This is the bit I’m most confused about, when trying to create my own:

typealias CallbackDelegateType = @convention(c) (UnsafePointer<CChar>) -> Void

var sCallbackDelegate: CallbackDelegateType? = nil

// Declared in C# as: static extern void SetNativeCallback(CallbackDelegate callback);
@_cdecl("SetNativeCallback")
func setNativeCallback(_ delegate: CallbackDelegateType)
{
    print("############ SET NATIVE CALLBACK")
    sCallbackDelegate = delegate
}

// This is a function for your own use from the enclosing Unity-VisionOS app, to call the delegate
// from your own windows/views (HelloWorldContentView uses this)
public func CallCSharpCallback(_ str: String)
{
    if (sCallbackDelegate == nil) {
        return
    }

    str.withCString {
        sCallbackDelegate!($0)
    }
}

Could anyone let me know how I can create a callback that receives for example a string, a float and an int parameters?
Thank you!!

2

Try:

typealias CallbackDelegateType = @convention(c) (UnsafePointer<CChar>, Float, Int32) -> Void

var sCallbackDelegate: CallbackDelegateType? = nil

@_cdecl("SetNativeCallback")
func setNativeCallback(_ delegate: CallbackDelegateType)
{
    sCallbackDelegate = delegate
}

public func CallCSharpCallback(_ str: String, _ floatValue: Float, _ intValue: Int32)
{
     if (callbackDelegate == nil) {
         return
     }
 
     str.withCString {
         callbackDelegate!($0, floatValue, intValue)
     }
}

On the C# side:

delegate void CallbackDelegate(string command, float floatValue, int intValue);

static void CallbackFromNative(string command, float floatValue, int intValue)
{
    // ...
}

C#'s int type is 32 bits, whereas Swift’s Int is 64 bits on 64 bit platforms (like visionOS), so you have to explicitly use Int32 in Swift.

3

ah so simple, thank you! still picking Swift up. will implement now and let you know how it goes

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4

thanks again @kapolka , got SwiftUI working great and I’m using it for most of my debug panels… here’s one example, to play with PBR values:
PBR SwiftUI panel

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