C#•2y ago

✅ Which is the more correct way of class instantiation?

// app.axaml.cs
public override void OnFrameworkInitializationCompleted()
{
    if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
    {
        Helpers hp = new();

        desktop.MainWindow = new MainWindow
        {
            DataContext = new MainWindowViewModel(hp),
        };
    }

    base.OnFrameworkInitializationCompleted();
}

// app.axaml.cs
public override void OnFrameworkInitializationCompleted()
{
    if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
    {
        Helpers hp = new();

        desktop.MainWindow = new MainWindow
        {
            DataContext = new MainWindowViewModel(hp),
        };
    }

    base.OnFrameworkInitializationCompleted();
}

// app.axaml.cs
public override void OnFrameworkInitializationCompleted()
{
    if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
    {
        Helpers hp = new();

        desktop.MainWindow = new MainWindow
        {
            DataContext = new MainWindowViewModel(hp),
        };
    }

    base.OnFrameworkInitializationCompleted();
}

// app.axaml.cs
public override void OnFrameworkInitializationCompleted()
{
    if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
    {
        Helpers hp = new();

        desktop.MainWindow = new MainWindow
        {
            DataContext = new MainWindowViewModel(hp),
        };
    }

    base.OnFrameworkInitializationCompleted();
}

// MainWindowViewModel.cs
public class MainWindowViewModel : ViewModelBase
{
  private Helpers _hp = new();

  // this part is 100% optional. You can use helpers as _hp as well
  public Helpers Hp
  {
      get => _hp;
      set => this.RaiseAndSetIfChanged(ref _hp, value);
  }
}

// MainWindowViewModel.cs
public class MainWindowViewModel : ViewModelBase
{
  private Helpers _hp = new();

  // this part is 100% optional. You can use helpers as _hp as well
  public Helpers Hp
  {
      get => _hp;
      set => this.RaiseAndSetIfChanged(ref _hp, value);
  }
}

// MainWindowViewModel.cs
public class MainWindowViewModel : ViewModelBase
{
  private Helpers _hp = new();

  // this part is 100% optional. You can use helpers as _hp as well
  public Helpers Hp
  {
      get => _hp;
      set => this.RaiseAndSetIfChanged(ref _hp, value);
  }
}

// MainWindowViewModel.cs
public class MainWindowViewModel : ViewModelBase
{
  private Helpers _hp = new();

  // this part is 100% optional. You can use helpers as _hp as well
  public Helpers Hp
  {
      get => _hp;
      set => this.RaiseAndSetIfChanged(ref _hp, value);
  }
}

Is it better to instantiate your used objects like this in the

app.axaml.cs

app.axaml.cs

app.axaml.cs

app.axaml.cs file and then pass them off to the main window view model like the public override function at the top or is it better to instantiate your used objects in the main window view model like the code block underneath it? I ask because I've noticed that when I build a new view model, if I instantiate the items I need right there in the class as new instances of that item, I don't have the need for two constructors like

public MainWindowViewModel()
{
    Text = "Hello World!";
}
public MainWindowViewModel(Helpers hp)
{
    _hp = hp;
}

public MainWindowViewModel()
{
    Text = "Hello World!";
}
public MainWindowViewModel(Helpers hp)
{
    _hp = hp;
}

public MainWindowViewModel()
{
    Text = "Hello World!";
}
public MainWindowViewModel(Helpers hp)
{
    _hp = hp;
}

public MainWindowViewModel()
{
    Text = "Hello World!";
}
public MainWindowViewModel(Helpers hp)
{
    _hp = hp;
}

so I'm just curious to if it's user preference, or which is more correct

Pobiega•3/14/24, 7:06 PM

Depends on a few things. First, the parameterless constructor implies that the helper object is optional

Pobiega•3/14/24, 7:06 PM

But it's not declared as such, so that's an orange flag.

Pobiega•3/14/24, 7:07 PM

However, beyond that it's really up to you if you want to do inversion of control or not

MekOP•3/14/24, 7:07 PM

the only reason I have two constructors is because when I pass variables from the previous file to the next file, I get an error saying that the view model can't find a good enough constructor

MekOP•3/14/24, 7:07 PM

I forgot to put the : this(): this() on the one that is supposed to be called

Pobiega•3/14/24, 7:07 PM

Taking the dependency as a constructor parameter let's you easily use DI for example

Pobiega•3/14/24, 7:08 PM

But if you dont plan on using DI, there isn't much to win

MekOP•3/14/24, 7:08 PM

DI means dependency injection, right?

Pobiega•3/14/24, 7:08 PM

Yup

MekOP•3/14/24, 7:09 PM

so passing the instance from app.axaml.cs to MWVM is DI when I use that passed object in the MWVM

MekOP•3/14/24, 7:10 PM

ok so I'm still not quite satisfied. Which is better? DI or new instantiations in each view model and other classes (creating multiple instances)?

Pobiega•3/14/24, 7:10 PM

Depends. Does the helper class have internal state that shouldn't be mixed across multiple windows?

Pobiega•3/14/24, 7:10 PM

If it does, don't inject the same instance

Pobiega•3/14/24, 7:11 PM

If it doesn't, can the helper be static?

MekOP•3/14/24, 7:11 PM

public class Helpers
{
    private static readonly string _tosPath = Directory.GetCurrentDirectory() + "/MakeMyProject/TermsOfService.txt";

    internal string GetTosText()
    {
        var fileData = File.ReadAllText(_tosPath);

        if (fileData != null)
        {
            return fileData;
        }
        else
        {
            return """
                    No Tos Text Was Found

                    If you believe this to be in error then try restarting
                    the program, otherwise, please create a new issue on
                    the github repo page.

                    -Mekasu
                   """;
        }
    }
}

public class Helpers
{
    private static readonly string _tosPath = Directory.GetCurrentDirectory() + "/MakeMyProject/TermsOfService.txt";

    internal string GetTosText()
    {
        var fileData = File.ReadAllText(_tosPath);

        if (fileData != null)
        {
            return fileData;
        }
        else
        {
            return """
                    No Tos Text Was Found

                    If you believe this to be in error then try restarting
                    the program, otherwise, please create a new issue on
                    the github repo page.

                    -Mekasu
                   """;
        }
    }
}

this is one of my helper files. The other one is a JsonEngine which is a public class with internal functions

Pobiega•3/14/24, 7:19 PM

This one seems as if it could be static, techically

Pobiega•3/14/24, 7:19 PM

but if we disregard that and speak about the concept generally, I'd usually recommend passing them in via the constructor, as it gives more freedom

Pobiega•3/14/24, 7:20 PM

you can tweak what VMs share what dependencies as you need - new every time, partial sharing, full sharing, etc

MekOP•3/14/24, 7:20 PM

gotcha. thanks!

PPobiega This one seems as if it could be static, techically

MekOP•3/14/24, 7:27 PM

just to be sure I understand the lingo.

This one seems as if it could be static, technically

public class MainWindowViewModel : ViewModelBase
{
  ViewModelBase _content = new();

- private Helpers _hp = new();
- private JsonEngine _jsEngine = new();

- public MainWindowViewModel(Helpers hp, JsonEngine jsEngine)
+ public MainWindowViewModel()
  {
-    UsersModel model = JsEngine.CreateUsersFile();
+    UsersModel model = JsonEngine.CreateUsersFile();
  }

- public Helpers Hp
- {
-    get => _hp;
-    set => this.RaiseAndSetIfChanged(ref _hp, value);
- }

- public JsonEngine JsEngine
- {
-    get => _jsEngine;
-    set => this.RaiseAndSetIfChanged(ref _jsEngine, value);
- }
}

public class MainWindowViewModel : ViewModelBase
{
  ViewModelBase _content = new();

- private Helpers _hp = new();
- private JsonEngine _jsEngine = new();

- public MainWindowViewModel(Helpers hp, JsonEngine jsEngine)
+ public MainWindowViewModel()
  {
-    UsersModel model = JsEngine.CreateUsersFile();
+    UsersModel model = JsonEngine.CreateUsersFile();
  }

- public Helpers Hp
- {
-    get => _hp;
-    set => this.RaiseAndSetIfChanged(ref _hp, value);
- }

- public JsonEngine JsEngine
- {
-    get => _jsEngine;
-    set => this.RaiseAndSetIfChanged(ref _jsEngine, value);
- }
}

right?

Pobiega•3/14/24, 7:32 PM

Yeah, pretty much

MekOP•3/14/24, 7:50 PM

ok bet. ty

✅ Which is the more correct way of class instantiation?

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