Local File System about camelotia

[gamidon]

I implemented the feature, it works fine, but now I have to use the null coalescing operator on
_open = ReactiveCommand.Create( () => Path.Combine(CurrentPath ?? _provider.InitialPath, SelectedFile.Name), canOpenCurrentPath, mainThread);
This is due to retracing _back. Eventually you can return to the null value. I don't know how to set a value to CurrentPath that initializes it from the constructor and never lets it be null. If there is a way please let me know how. If not this is way more work than it is solving as now I am chasing that null it can hit at run time.

Totally appreciate any idea on how best to solve this, right now it is a really poor way to handle CurrentPath and error prone at run time. The resulting code is more dangerous than just using a private set since and future changes will not necessarily understand that the value can return to null. I was surprised when I got hit with it.

I will Pull request soon so you can take a look.
Thanks,
Greg

[gamidon]

About the null. I was referring to the fact that on startup:
public string CurrentPath => _currentPath?.Value; is uninitialized and in fact null.
You already are managing around this null. If you remove the Elvis operator from this:
public string CurrentPath => _currentPath?.Value; an exception will be thrown.

I am not a fan of the FodyWeavers for this because I cannot easily determine or breakpoint when a field is set. So reading code to find the actual set is more time consuming and if I wanted to break on all set calls I have to find all the places it might actually be set. So if a field changed unexpectedly somewhere in the code trapping that is made more difficult. I think using set with RaiseAndSetIfChanged is one additional line per field that is worth it. You can always make it a private set and get the same data security as Fody. Fody just changes a private set with a reflection set and does not prohibit multiple calls in the viewmodel from stepping on each other. The fody way removes the one path to set and created multiple paths to set. Just a personal preference.... Everyone has there own :) When "Magic" happens its always harder to debug when something goes wrong.

[worldbeater]

Good day @gamidon and thank you for your contribution.

I agree the issue you describe exists and should be resolved. I think introducing a new IProvider.InitialPath property could be a better option, with such property we could let the providers decide where to start displaying files on their own.

Then, for most cloud file storages, the IProvider.InitialPath property should be / and for local file storage it'll be something like drives or my-computer or something like that (using nulls as valid values generally doesn't seem to be a good idea, and here is explained why).

I would really appreciate if you could provide an implementation for this. Might be worth opening a work-in-progress PR to avoid merge conflicts etc.

[worldbeater]

I see your point, thanks! Worth mentioning that Fody doesn't actually modify those get-only properties. The ObservableAsPropertyHelper<T> is a ReactiveUI feature, Fody uses code generation only for properties marked with [Reactive] attribute. I prefer OAPHs because of their immutability, OAPH properties always reflect latest values that have been sent through an IObservable stream. This allows us to describe relations among properties and commands declaratively and "express the idea around a feature in one readable place", the app won't compile if the developer accidentally tries to mutate a property in a non-reactive manner. Elvis operator is used for CurrentPath property because that property is used inside a WhenAny call before the CurrentPath property is initialized, I can admit it's kind of a hack to avoid dealing with mutable state where it is not entirely neccessary. :) So I agree that sometimes using nulls is a necessary evil, but if there is a chance to avoid that, it's worth trying.

[worldbeater]

@gamidon the solution you are looking for is passing the InitialPath value to ObservableAsPropertyHelper that controls the CurrentPath property. You need to pass the InitialPath value as a parameter to a .ToProperty call, the parameter name is initialValue. An example:

 _currentPath = pipeline
    .ToProperty(this, x => x.CurrentPath, initialValue: provider.InitialPath); // *

Docs. Another option is doing:

public string CurrentPath => _currentPath?.Value ?? "defaultValue";

[worldbeater]

Closing this as resolved by #6

Thanks @gamidon ❤️ 👍

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