How to store a pointer to class contructor

[Jacob Carlborg]

On Thursday, 24 December 2020 at 10:23:09 UTC, Dmitriy Asondo 
wrote:

> I expect code like this:
> ----------------------
> class OloloService {}
> class BlablaService {}
>
> auto servicesList = [OloloService, BlablaService];
> auto serviceInstance = new servicesList[1](args);
> ----------------------

Here's a slightly different version that I think is closer to 
your original example:

import std;

interface Service {}

mixin template Constructor()
{
     this(int a)
     {
     }
}

class OloloService : Service
{
     mixin Constructor;
}

class BlablaService : Service
{
     mixin Constructor;
}

Service function(int) create(T)()
{
     return a => new T(a);
}

void main()
{
     auto servicesList = [create!OloloService, 
create!BlablaService];
     auto serviceInstance = servicesList[1](3);
     writeln(serviceInstance);
}

Since D is a statically typed language you need a form of base 
type if you want to store a list of values of different types. In 
this case, the base type is `Service`. If you want to have a 
constructor, as you do in your original example, the constructor 
needs to have the same signature for all types, the mixin 
template helps with that.

You can use a tuple as well to store different values of 
different types. But then everything need to be known at compile 
time. That is, the index, in your case.

--
/Jacob Carlborg