C#•5mo ago

Is it possible to change the return type of interface method to the type of the implementing struct?

Say I have the following code:

interface IBiggerThan
{
    public abstract IBiggerThan GetBiggest(IBiggerThan compareTo);
}
struct A : IBiggerThan
{
    float _a;
    public A GetBiggest(A compareTo)
    {
        if (this._a > compareTo._a)
            return this;
        return compareTo;
    }
}
struct B : IBiggerThan
{
    float _b;
    public B GetBiggest(B compareTo)
    {
        if (this._b > compareTo._b)
            return this;
        return compareTo;
    }
}

interface IBiggerThan
{
    public abstract IBiggerThan GetBiggest(IBiggerThan compareTo);
}
struct A : IBiggerThan
{
    float _a;
    public A GetBiggest(A compareTo)
    {
        if (this._a > compareTo._a)
            return this;
        return compareTo;
    }
}
struct B : IBiggerThan
{
    float _b;
    public B GetBiggest(B compareTo)
    {
        if (this._b > compareTo._b)
            return this;
        return compareTo;
    }
}

I want to have GetBiggest return an instance of the struct its implemented within. This code obviously won't compile, but I'm wondering if there's a way to implement the intent behind it. I want to avoid returning object or IBiggerThan and then casting it wherever this method gets called, instead I want the return type to explicitly be that of the implementing struct. Is this possible, or am I missing something important?

3 Replies

Sossenbinder•5mo ago

Are you looking for the CRTP by chance? https://blog.stephencleary.com/2022/09/modern-csharp-techniques-1-curiously-recurring-generic-pattern.html

Modern C# Techniques, Part 1: Curiously Recurring Generic Pattern

The curiously recurring generic pattern, where a base type or interface has its derived type as a generic parameter. Part of a series looking at modern C# code techniques.

EvyrOP•5mo ago

I think so, thanks turns out I went down a similar line to this about 30 minutes ago but misused generics and threw errors

Sossenbinder•5mo ago

Neat. I think it's a good idea in this case anyways, since with a interface-based return type you'll run into boxing behavior when working with structs

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Is it possible to change the return type of interface method to the type of the implementing struct?