Re: How to make a generic function to take a class or struct by reference?

[vit via Digitalmars-d-learn]

On Sunday, 27 March 2022 at 16:27:44 UTC, JN wrote:

I would like to have only one definition of getX if possible, because they both are doing the same thing. I can't remove the ref one, because without a ref it will pass the struct as a temporary and compiler won't like that.

```d
import std.stdio;

struct Foo
{
    int x;

    void doStuff()
    {
        *getX(this) = 5;
    }
}

class Bar
{
    int x;

    void doStuff()
    {
        *getX(this) = 5;
    }
}

int* getX(T)(ref T t)
{
    return &t.x;
}

int* getX(T)(T t)
{
    return &t.x;
}

void main()
{
    Foo foo;
    Bar bar = new Bar();

    foo.doStuff();
    bar.doStuff();

    assert(foo.x == 5);
    assert(bar.x == 5);
}
```

Try this:
```d

int* getX(T)(return auto ref T t){
        static if(is(T == class))
                return &t.x;
        else static if(is(T == struct) && __traits(isRef, t))
                return &t.x;
        else
                static assert(0, "no impl " ~ T.stringof);
}
```
or:

```d

int* getX(T)(return auto ref T t)
if(is(T == class) || (is(T == struct) && __traits(isRef, t))){
        return &t.x;
}
```