C#•14mo ago

✅ Issues with interfaces and generic classes

I want to create a general-practise chemistry model in C#. I have created some basic objects and created a few interfaces to specify the interactions between the classes. Now I have an issue when trying to create an instance with a generic class only allowing a certain interface. I have attached a picture to make the relations a bit clearer. Now for the issue Compound implements ISolute as well as IAmount I now pack it into the Mol class which looks like this

public class Mol<IAmount>
{
    public double Amount { get; set; }
    public required IAmount Compound { get; set; }

    public static Mol<IAmount> Of(IAmount compound, double amount)
    {
        return new Mol<IAmount>() { Amount = amount, Compound = compound };
    }
}

public class Mol<IAmount>
{
    public double Amount { get; set; }
    public required IAmount Compound { get; set; }

    public static Mol<IAmount> Of(IAmount compound, double amount)
    {
        return new Mol<IAmount>() { Amount = amount, Compound = compound };
    }
}

Which works fine since compound implements it. Now I want to create a solution out of it with this method of the solution class:

    public static Solution Of(Mol<ISolute> solute, Volume<ISolvent> solvent)
    {
        return new Solution() { Solute = solute, Solvent = solvent };
    }

    public static Solution Of(Mol<ISolute> solute, Volume<ISolvent> solvent)
    {
        return new Solution() { Solute = solute, Solvent = solvent };
    }

Where the problem arises of the ISolute interface not corresponding with the type Compound eventhough ISolute is implemented by Compound and inherits from IAmount

48 Replies

Jona4PlayOP•14mo ago

Also just for reference this is the corresponding unit test

[<Fact>]
let ``Create a 1M solution of H2SO4 in water`` () =
    let sulfuricAcid = Mol.Of(new Compound("Sulfuric acid", "H2SO4"), 1)
    let water = Volume.Of(new Compound("Water", "H2O"), 1)
    let solution = Solution.Of(sulfuricAcid, water)
    Assert.Equal(1.0, solution.Concentration)

[<Fact>]
let ``Create a 1M solution of H2SO4 in water`` () =
    let sulfuricAcid = Mol.Of(new Compound("Sulfuric acid", "H2SO4"), 1)
    let water = Volume.Of(new Compound("Water", "H2O"), 1)
    let solution = Solution.Of(sulfuricAcid, water)
    Assert.Equal(1.0, solution.Concentration)

This shows a pre compile error for both ISolute and ISolvent

Luxx•14mo ago

I don’t see that compound implements Amount from ISolute The chemist in me also suggests renaming “Concentration” to “Molality”?

DΣX•14mo ago

i dont think i fully understand, but what if u create interface ICompound, implement IAmount and ISolute in it. use the new interface anywhere where u r having the compound. will this solve your problem?

Jona4PlayOP•14mo ago

The interfaces are empty as of now. Maybe I misunderstood you. Also yes. Renaming to molarity makes sense Not sure but dont think so. Both ionized Elements and Compounds can be Solutes. Only compounds can be solvents. And both can be taken quantities of in Mol. That's why I thought I'd have the Mol generic as a wrapper around it which entails the quantity in addition to some IAmount of element or compound. But extracting that to a new ICompound interface makes sense

Jona4PlayOP•14mo ago

This is the updated diagram

DΣX•14mo ago

i really have no idea about chemistry, and even less so in english. so just inform me if that helps in any way. i wouldnt understand just by the diagram 😄

Thinker•14mo ago

Also you're writing your tests in F#?

DΣX•14mo ago

wait, this is f#? you can name functions with complex strings in f#? 😄

Thinker•14mo ago

yea

Jona4PlayOP•14mo ago

Yes XD

Thinker•14mo ago

is that the only reason you're using F#...?

Jona4PlayOP•14mo ago

Nope. Just learned to love the language. Also less boilerplate because I already hate writing unit tests

Thinker•14mo ago

makes sense

Jona4PlayOP•14mo ago

Oh do I see lambda calc in your bio?

Thinker•14mo ago

ye I'm working on a lambda calc repl in Haskell for fun Haven't used F# a ton but wanna try it out more tbh

Jona4PlayOP•14mo ago

Great to get work done quick. Kinda like python, although it has on par modeling ability with C#

Thinker•14mo ago

Yeah can see that Anyway sorry for diverting the thread

Jona4PlayOP•14mo ago

All good. Im working on a different part. Hoping a good idea pops up Might add a github link too. Maybe it's beneficial to actually have others see the shit code I wrote

Jona4PlayOP•14mo ago

https://github.com/Jonathan-Schaefer-git/DotChem

GitHub

GitHub - Jonathan-Schaefer-git/DotChem

Contribute to Jonathan-Schaefer-git/DotChem development by creating an account on GitHub.

Luxx•14mo ago

Sorry, I misunderstood the Diagram. I read the IAmount as a property Amount. I’m can tell from the diagram alone why it wouldn’t resolve. Is there a specific compile error?

Jona4PlayOP•14mo ago

Nope. Sadly not. I honestly dont quite understand the error. It says that there is a type mismatch. I suspect it being the use of the Mol<IAmount> Wrapper class causing this

Luxx•14mo ago

If you remove ISolvent from ICompound, does it work?

Jona4PlayOP•14mo ago

Just says Mol<Compound> is not compatible with Mol<ISolute> eventhough Compound implements both IAmount and ISolute No. Same error Maybe there is a way around this

Luxx•14mo ago

Try to simplify it in another project with just IMol, ICompound, and IAmount? Add one interface at a time.

Jona4PlayOP•14mo ago

Ok sure. That makes sense 👍

Omnissiah•14mo ago

Just says Mol<Compound> is not compatible with Mol<ISolute>

bot Mol<> is not extending anything Mol<type1> is not compatible with Mol<type2> whatever the case they are two different types not even the generic type of Mol<> has a constraint

Jona4PlayOP•14mo ago

But ISolute inherits IAmount

Omnissiah•14mo ago

bit Mol doesn't know it

Jona4PlayOP•14mo ago

Well shit. How would you correct for that?

Omnissiah•14mo ago

maybe class Mol<T> where T:ICompound

Luxx•14mo ago

Was about to suggest this as well

Omnissiah•14mo ago

yeah although inheritance is not the easiest thing to deal with

Jona4PlayOP•14mo ago

Thing is though, that this isnt possible. It should be the IAmount interface as mol of elements are possible. So should I change it to IAmount? Wouldn't this have the same issue with interface inheritance as beforehand?

Omnissiah•14mo ago

use whatever the base interface is i put ICompound there but not with the entire knowledge of the project ah ok i read the diagram in reverse

Jona4PlayOP•14mo ago

ok give me a minute Yeah arrows are fucked up. It the VS designer thing Ok. I believe I messed up, as it shows the same thing but with it now being broader the error changed

public class Mol<T> where T:IAmount

public class Mol<T> where T:IAmount

Is the header for the Mol class But its now Mol<IAmount> is not compatible with Mol<ISolute> Which means its still doesnt recognize the inheritance of the interface

    let a = Mol.Of(new Compound("", ""), 1)
    let b : Mol<ISolute> = Mol.Of(new Compound("", ""), 1)

    let a = Mol.Of(new Compound("", ""), 1)
    let b : Mol<ISolute> = Mol.Of(new Compound("", ""), 1)

This has the same error

Omnissiah•14mo ago

because they still are two different types you would have to make Mol inherit from something not generic or use the same generic type

Jona4PlayOP•14mo ago

I... dont think I fully understand what you mean by that. Could you please elaborate or give me an example?

Omnissiah•14mo ago

(basically it means class Mol<IAmount> : IMol, so that IMol m could hold every Mol<>, then you cast as needed; if you look at c# collections they have a common non-generic inheritance) as Luxx said, i would just try starting with Mol with no generics, since at the moment it doesn't seem you need it if you then need more, then you probably should read about covariance and contravariance but i would try to stay as simple as possible

Jona4PlayOP•14mo ago

Ok thanks

Omnissiah•14mo ago

still, this should work

var a = Mol<IAmount>.Of(new Compound1("", ""), 1);
var b = Mol<IAmount>.Of(new Compound2("", ""), 2);
a = b;
var c = Mol<IAmount>.Of(new Solute3(), 3);
a = c;

var a = Mol<IAmount>.Of(new Compound1("", ""), 1);
var b = Mol<IAmount>.Of(new Compound2("", ""), 2);
a = b;
var c = Mol<IAmount>.Of(new Solute3(), 3);
a = c;

but it's kinda delicate and if you screw up it could throw exception at runtime

Jona4PlayOP•14mo ago

Yeah this would work. But I think I'll try the approach you described first

g00dSoup•14mo ago

What tool did you use to create the diagram? Looks so neat

Jona4PlayOP•14mo ago

Visual Studio Class Designer. Its installable through the VS installer just drag in a whole project and it auto generates it

g00dSoup•14mo ago

Jona4PlayOP•14mo ago

I have implemented a simpler working version, although I'd like to pick up the Generic version tomorrow

Accord•14mo 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.

Jona4PlayOP•14mo ago

Thanks to everyone @here. Thanks to your input I was able to figure it out 👍

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✅ Issues with interfaces and generic classes