C#•2y ago

Generics and type inference

    public TDest MapTo<TSource, TDest>(TSource src)
    {
        var res = _mapper.Map<TSource, TDest>(src);
        return res; 
    }

    public TDest MapTo<TSource, TDest>(TSource src)
    {
        var res = _mapper.Map<TSource, TDest>(src);
        return res; 
    }

Why can't the compiler infer my type of TSource? If I call that mehod I always have to specify it like this

Mapper.MapTo<ObjectA, ObjectB>(instance of ObjectA);

Mapper.MapTo<ObjectA, ObjectB>(instance of ObjectA);

It should be possible to call it just like this

Mapper.MapTo<ObjectB>(instance of ObjectA);

Mapper.MapTo<ObjectB>(instance of ObjectA);

I am just starting with .NET

8 Replies

Thinker•2y ago

There is no partial inference, you either have to specify all or no generic parameters. And yes this is annoying

nobody•2y ago

Oh that sucks I love using generics to simplify code, anyway thank you for your quick help!

Thinker•2y ago

language do you come from btw?

nobody•2y ago

@thinker227 I did most of my work with python/c++ and recently very much with Haskell (loving it) - whats your main language?

Thinker•2y ago

C# but also doing a bit of Haskell occasionally. Was just wondering what language you were using if you were expecting this kind of partial generic inference. C#'s type system is unfortunately nowhere as sophisticated as Haskell's or what you can do with C++ templates.

nobody•2y ago

Yeah its from my experiences with C++ templates and especially Haskell I just like working with strong typesystems. btw thats why Rust is simply awesome imho

Thinker•2y ago

Fair point Compared to a lot of other ones, C#'s type system is quite tame.

nobody•2y ago

True in comparsion, but its fine C# has some nice features too like record types which I've just learned about. I'm starting to try build up a github profile with some showcases thats why I try to learn different techs (webAPI in the C# case)

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Generics and type inference