C#•2y ago

❔ Class with parameter as a generic parameter

Hi! I'm trying to write a navigation system in wpf My setup rn using default constructor is

public class ViewModelBase : INotifyPropertyChanged {
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName) {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public virtual void Dispose() { }
}

public class ViewModelBase : INotifyPropertyChanged {
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName) {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public virtual void Dispose() { }
}

public class NavigationService<TViewModel> where TViewModel : ViewModelBase {
    private readonly NavigationStore _navigationStore;
    private readonly Func<TViewModel> _createViewModel;

    public NavigationService(NavigationStore navigationStore, Func<TViewModel> createViewModel) {
        _navigationStore = navigationStore;
        _createViewModel = createViewModel;
    }

    public void Navigate() {
        _navigationStore.CurrentViewModel = _createViewModel();
    }
}

public class NavigationService<TViewModel> where TViewModel : ViewModelBase {
    private readonly NavigationStore _navigationStore;
    private readonly Func<TViewModel> _createViewModel;

    public NavigationService(NavigationStore navigationStore, Func<TViewModel> createViewModel) {
        _navigationStore = navigationStore;
        _createViewModel = createViewModel;
    }

    public void Navigate() {
        _navigationStore.CurrentViewModel = _createViewModel();
    }
}

however i want to change it so each ViewModelBase has a public custom constructor like TViewModel.NavigateTo() that returns its instance to be able to define some common logic between navigables I've tried to do

public interface Navigable<TViewModel> where TViewModel : ViewModelBase {
    TViewModel NavigatedTo();
}

public interface Navigable<TViewModel> where TViewModel : ViewModelBase {
    TViewModel NavigatedTo();
}

public class NavigationService<Navigable<TViewModel>> where TViewModel : ViewModelBase {

public class NavigationService<Navigable<TViewModel>> where TViewModel : ViewModelBase {

but it breaks

7 Replies

Sossenbinder•2y ago

How does it break? Are you attempting to call .NavigatedTo() within your NavigationService?

cathei•2y ago

Is there reason you can't do this?

public class NavigationService<TViewModel> where TViewModel : ViewModelBase
{
   public NavigationService(NavigationStore navigationStore, INavigable<TViewModel> navigable) { /* ... */ }
}

public class NavigationService<TViewModel> where TViewModel : ViewModelBase
{
   public NavigationService(NavigationStore navigationStore, INavigable<TViewModel> navigable) { /* ... */ }
}

IndeedOP•2y ago

In the typing itself

cathei•2y ago

Do you want this?

public class NavigationService<TViewModel>
  where TViewModel : ViewModelBase, INavigable<TViewModel>

public class NavigationService<TViewModel>
  where TViewModel : ViewModelBase, INavigable<TViewModel>

IndeedOP•2y ago

gimme a sec to follow this train of thought in ym code oh, seems right Yes! It works thank you! ❤️

cathei•2y ago

Yay

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Class with parameter as a generic parameter