C#•2y ago

How to use Tuple in generic class?

So I know you can use Tuple<Type, Func<object>> for example, but is there any way to just use (Type type, Func<Object> obj)? Or even give Tuple<> names so it isn't Item1, Item2? I imagine if this isn't implemented it has to do with how the () tuple works at compile, but I would think it is easy enough on compile time to just do .ToTuple() wherever it would be needed.

20 Replies

Klarth•2y ago

You should typically avoid Tuple<...> as it's the old reference type. Use ValueTuple<...> with the newer syntax. eg. (Type Type, Func<object> Function) tuple = (typeof(Program), () => 5); Unfortunately, I don't think you can use var here and name the right-hand side. https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/value-tuples#tuple-field-names You could otherwise in tuples that don't have lambdas.

Klarth•2y ago

You get this error if you try only the RHS.

Chiyoko_S•2y ago

there is a tuple notation in C# that you can use, but that is not Tuple<>, it's actually ValueTuple<> (which for our purposes should do the same thing) and you can actually use var and name elements from the RHS (Type: a, Function: b)

Xan.Nava•2y ago

Not sure how to do that with Generic. For example

public interface Iam<T, TR> {
    public T TestMethod(TR value);
}

public class ClassName : Iam<Type, ValueTuple<int, string>> {
    public Type TestMethod((int, string) value) {
        // Do Stuff

        return value.Item1.GetType();
    }
}

public interface Iam<T, TR> {
    public T TestMethod(TR value);
}

public class ClassName : Iam<Type, ValueTuple<int, string>> {
    public Type TestMethod((int, string) value) {
        // Do Stuff

        return value.Item1.GetType();
    }
}

Is what I am getting with ValueType, but if I put (itn: age, string: name) it throws errors.

Chiyoko_S•2y ago

well what is the actual code that shows error and what error

Xan.Nava•2y ago

public Type TestMethod((int value, string name) value)

public Type TestMethod((int value, string name) value)

throws

Severity    Code    Description    Project    File    Line    Suppression State
Error    CS8141    The tuple element names in the signature of method 'ClassName.TestMethod((int value, string name))' must match the tuple element names of interface method 'Iam<Type, (int, string)>.TestMethod((int, string))' (including on the return type).    UniversalUnity    F:\sys0\DreamScaping_Unity\Assets\Packages_Internal\Levels\UniversalUnity\Level1\Physics\Collisions\Collisions.Interchange.cs    276    Active

Severity    Code    Description    Project    File    Line    Suppression State
Error    CS8141    The tuple element names in the signature of method 'ClassName.TestMethod((int value, string name))' must match the tuple element names of interface method 'Iam<Type, (int, string)>.TestMethod((int, string))' (including on the return type).    UniversalUnity    F:\sys0\DreamScaping_Unity\Assets\Packages_Internal\Levels\UniversalUnity\Level1\Physics\Collisions\Collisions.Interchange.cs    276    Active

Klarth•2y ago

I would use a concrete type there, not a tuple. Especially in Unity where C# is weaker.

Xan.Nava•2y ago

Severity    Code    Description    Project    File    Line    Suppression State
Error    CS0246    The type or namespace name 'age' could not be found (are you missing a using directive or an assembly reference?)    UniversalUnity    F:\sys0\DreamScaping_Unity\Assets\Packages_Internal\Levels\UniversalUnity\Level1\Physics\Collisions\Collisions.Interchange.cs    276    Active

Severity    Code    Description    Project    File    Line    Suppression State
Error    CS0246    The type or namespace name 'age' could not be found (are you missing a using directive or an assembly reference?)    UniversalUnity    F:\sys0\DreamScaping_Unity\Assets\Packages_Internal\Levels\UniversalUnity\Level1\Physics\Collisions\Collisions.Interchange.cs    276    Active

is for

public Type TestMethod((int: age, string: name) value)

public Type TestMethod((int: age, string: name) value)

blokyk•2y ago

It's because ValueTuple<int, string> is not quite the same as (int value, string name) so you need to write

public class ClassName : Iam<Type, (int value, string name)>
{ ... }

public class ClassName : Iam<Type, (int value, string name)>
{ ... }

Xan.Nava•2y ago

Ah yep that is working now. Not sure where I was bonking it up yesterday 😆

public class ClassName : Iam<Type, (int age, string name)>

public class ClassName : Iam<Type, (int age, string name)>

Chiyoko_S•2y ago

I think it's really just complaining why you don't have names matched up yeah

Xan.Nava•2y ago

I am working in unity so maybe the (int: age, string: name) is a newer C# way? the (int age, string name) works fine.

Chiyoko_S•2y ago

no it's like two different things I think I understood your question as 'how to name tuple elements on construction using var' in which case you can do var a = (Name: "hello", Age: 20);

blokyk•2y ago

i don't think (int: arg, string: name) is valid for a declaration, and even if it was var t = (int: age, string: name) where age and name already exists, int and strings are keywords so it wouldn't work

Xan.Nava•2y ago

Cool cool, thanks for the help!

Chiyoko_S•2y ago

also Klarth's point is valid, tuples can be fine for some one-off stuffs but they get kinda long and cumbersome (somewhat) if you end up using it a lot records could be an alternative

blokyk•2y ago

i mean if they're using unity, they probably don't have records :/

Chiyoko_S•2y ago

oh crap runs

blokyk•2y ago

ye unity isn't great lol

Xan.Nava•2y ago

Yeah I am using it for some generic stuff that doesn't need a full command struct for the args, but need different number of args per inheritor.

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How to use Tuple in generic class?