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amay077
amay077

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Kotlin's scope functions in C#

#kotlin #csharp

Kotlin's scope functions(.let, .also, .apply, etc) are super useful.

I want to these methods in C#.
So I just define it!

static class ObjectExtensions 
{
    // Kotlin: fun <T, R> T.let(block: (T) -> R): R
    public static R Let<T, R>(this T self, Func<T, R> block) 
    {
        return block(self);
    }

    // Kotlin: fun <T> T.also(block: (T) -> Unit): T
    public static T Also<T>(this T self, Action<T> block)
    {
        block(self);
        return self;
    }   
}
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Usage 

var text = resultCode.Let(x => {
    switch (x) {
        case 0:
            return "success";
        default:
            return $"error({x})";
    }
});

var model = new MyModel().Also(m => {
    m.Initialize();
    m.Load(path);
});
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I hope .NET Framework provide these methods.

Top comments (4)

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petergabriel2 profile image
PeterGabriel2 • • Edited

Please, didn't you by chance ask Microsoft team when scope functions will be in C#?

C# really need this.

I have hard times to come back from Kotlin to C#. Kotlin is just so much more effective language.

I also miss keyword "val". It's just so elegant. And I would discard keyword "new".

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moljac profile image
moljac •

And after your suggestions are accepted and implemented the language will be called k# (keesharp, kosharp).

Why not suggesting here: github.com/dotnet/csharplang

I want multiple inheritance and templates like in C++ with specializations.

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solidogen profile image
Pat B. •

Those need to be fixed for folks trying to use them in Unity. It doesn't work well with Unity Objects, as generics erase their overridden equality check.

?. operator doesn't care about overridden equals
blogs.unity3d.com/2014/05/16/custo...

Working ones:

public static void Run<T>(this T self, Action<T> block)
{
    /* 
        Check if Unity Object was destroyed.
        "Destroyed" T as C# object is not null, but as UnityEngine.Object it will be null because of Equals override.
     */
    if ((UnityEngine.Object)(object)self == null)
    {
        return;
    }
    block(self);
}

public static R Let<T, R>(this T self, Func<T, R> block)
{
    /* 
        Check if Unity Object was destroyed.
        "Destroyed" T as C# object is not null, but as UnityEngine.Object it will be null because of Equals override.
     */
    if ((UnityEngine.Object)(object)self == null)
    {
        return default;
    }
    return block(self);
}

public static T Also<T>(this T self, Action<T> block)
{
    /* 
        Check if Unity Object was destroyed.
        "Destroyed" T as C# object is not null, but as UnityEngine.Object it will be null because of Equals override.
     */
    if ((UnityEngine.Object)(object)self == null)
    {
        return default;
    }
    block(self);
    return self;
}
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Now it is possible to safely call gameObject?.Run(...) without MissingReferenceException

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moljac profile image
moljac •

Nice. Thanks

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