Extracted interfaces from UndoService and ChangeFactory for IoC container registration

[danjoconnell]

Hi Nathan,

I was wanting to use Monitored Undo Framework in a Prism based project I’m working on, but Prism’s IoC functionality (like most others) seems to require services to have an interface abstraction for container registration and dependency injection.

To facilitate this, in this this pull request I’ve extracted interfaces from UndoService and ChangeFactory and moved XML documentation comments to the interfaces to avoid repetition. These interfaces also make it easier to mock UndoService and ChangeFactory in unit tests.

With these changes I can register UndoService and ChangeFactory with the IoC container by adding the following lines to the overriden RegisterTypes method in my application’s App.xaml.cs:

containerRegistry.RegisterInstance<MonitoredUndo.IUndoService>(MonitoredUndo.UndoService.Current);
containerRegistry.RegisterSingleton<MonitoredUndo.IChangeFactory, MonitoredUndo.ChangeFactory>();

Thank you for your time and consideration.

Regards,

Daniel O’Connell

[nathanaw]

Thanks Daniel! Will take a look this week.

[nathanaw]

A few questions and observations

1. I assume you're using Unity as the container for Prism? If so, I think you can use that with concrete types. I did a small test (below).
2. In reviewing the codebase, I think there are a few more changes we'd need if we moved it to an interface. There is code in the library that uses the UndoService.Current. That code would need to change so that it honored the interface. But that gets complicated, because we'd need to supply a mechanism to wire these up.
   • See UndoBatch line 32
   • See ChangeFactory lines 80 and 227

void Main()
{
	var undoService = MonitoredUndo.UndoService.Current;
	
	var container = new Unity.UnityContainer();
	
	container.RegisterInstance(undoService);
        // OR
	//container.RegisterFactory<UndoService>(c => undoService, FactoryLifetime.Singleton);
	
	var resolved = container.Resolve<UndoService>();
	Console.WriteLine("Resolved same container = {0}", ReferenceEquals(undoService, resolved));
}