ReactiveCommand.Execute not triggering IsExecuting

Question

I'm subscribed to the IsExecuting of a command:

LoginCommand.IsExecuting.Subscribe(x => Log("Logging in"));

and it works fine when my Command is invoked by InvokeCommand but when I call it by:

LoginCommand.Execute();

The IsExecuting observable is not triggered.

This works:

Observable.Start(() => { }).InvokeCommand(LoginCommand);

Does someone know why the IsExecuting property doesn't change when calling the Execute method? I'm trying to unit test the command so I thought this would be the best way to execute it from tests.

Answer 1

After the upgrade to ReactiveUI 7.0, the Execute() method changed. Right now it does not trigger the command immediately. Instead, it returns a cold IObservable to which you have to subscribe in order to make stuff happen.

LoginCommand.Execute().Subscribe();

Check in the write up about the changes in RxUI 7.0 in the release notes. Ctrl+F "ReactiveCommand is Better". It states explicitly:

the Execute exposed by ReactiveCommand is reactive (it returns IObservable). It is therefore lazy and won't do anything unless something subscribes to it.

Answer 2

When you want to execute an ReactiveCommand, you can do it like this:

RxApp.MainThreadScheduler.Schedule(Unit.Default, (scheduler, state) => 
       ViewModel.MyCommand.Execute(state).Subscribe());

You can then Subscribe to it like this:

this.WhenActivated(d => { 

    MyCommand
        .Select(_ => this)
        .ObserveOn(RxApp.MainThreadScheduler)
        .ExecuteOn(RxApp.TaskScheduler)
        .Subscribe(viewModel => {
            // ... 
        })
        .DisposeWith(d); 
});