MvvmCross Mvx.Trace usage

mono, mvvmcross, xamarin, xamarin.android, xamarin.ios

Solution

MvvmCross DebugTrace is all routed via a singleton implementation of `IMvxTrace`

Each platform provides different implementations of this:

- the Windows platforms use `Debug` trace (because `Trace` itself is not available on all the Windows platforms)

- Android uses a dual log of both `Debug` and the Android `log`

- iOS uses a dual log of both `Debug` and the iOS `Console`

This worked well in earlier versions of MvvmCross, especially where people linked directly to the MvvmCross source code and so could bind directly to either the debug or release MvvmCross binaries.

However... because people are now increasingly using the release Binaries from Nuget - in which `Debug` is of course compiled out, then this often leaves people asking "How to use it?"

The easiest way is for you to override the initialisation of IMvxTrace in your `Setup` class.

This is easy to do - e.g.:

   protected override IMvxTrace CreateDebugTrace() { return new MyDebugTrace(); }

where `MyDebugTrace` is something like:

public class MyDebugTrace : IMvxTrace
{
    public void Trace(MvxTraceLevel level, string tag, Func<string> message)
    {
        Debug.WriteLine(tag + ":" + level + ":" + message());
    }

    public void Trace(MvxTraceLevel level, string tag, string message)
    {
        Debug.WriteLine(tag + ":" + level + ":" + message);
    }

    public void Trace(MvxTraceLevel level, string tag, string message, params object[] args)
    {
        try
        {
            Debug.WriteLine(string.Format(tag + ":" + level + ":" + message, args));
        }
        catch (FormatException)
        {
            Trace(MvxTraceLevel.Error, tag, "Exception during trace of {0} {1} {2}", level, message);
        }
    }
}

If you wanted to include different implementations for debug/release; if you wanted to switch this on/off at runtime; if you wanted to filter on `MvxTraceLevel` or `tag`; or if you wanted to use some third party logging engine then this should also be easy to do using simple C# on each platform.

Problem

Original source