How to assign a param to a method in Reason - ocaml

Question

I have the following abstractFactory class:
class virtual virtualProductA = {
pub virtual methodA: string;
};
class virtual virtualProductB = {
pub virtual methodB: int;
};
class virtual abstractFactory = {
pub virtual createProductA : virtualProductA;
pub virtual createProductB : virtualProductB;
};
In particular, I would like to specify that the abstractFactory createProductA method has an optional param, that can be of any type.
Something along the lines of the following:
pub virtual createProductA (param?:any) : virtualProductA;
However, the above does not compile properly.
Any suggestions as to proper syntax is more than greatly appreciated. Thank you.

Answer 1

Disclaimer: I'm using OCaml. The Reason examples are translated using Try Reason.
I'm not sure I got your question right, but here are my thoughts on this.
If you want to give an argument to the constructor of your class virtualProductA, here the syntax.
OCaml
class virtual virtualProductA my_object = object
val value : 'a = my_object
method virtual methodA : string
end
Reason
class virtual virtualProductA my_object => {
as _;
val value: 'a = my_object;
pub virtual methodA: string;
};
In your abstract factory, the method createProductA now takes an argument and is polymorphic.
OCaml
class virtual abstractFactory = object
method virtual createProductA : 'a. 'a -> virtualProductA
method virtual createProductB : virtualProductB
end
Reason
class virtual abstractFactory = {
as _;
pub virtual createProductA: 'a. 'a => virtualProductA;
pub virtual createProductB: virtualProductB;
};
The type quantifier 'a. means "for all types 'a, ...". It is used to tell the compiler "This is not a type parameter, this is merely a polymorphic method".
On second thought, you will probably want to make virtualProductA generic, here's the syntax for that:
OCaml
class virtual ['a] virtualProductA my_object = object
val value : 'a = my_object
method value = value (* type 'a is inferred here, no need to over-annotate *)
method virtual methodA : string
end
Reason
class virtual virtualProductA 'a my_object => {
as _;
val value: 'a = my_object;
pub value = value; /* type 'a is inferred here, no need to over-annotate */
pub virtual methodA: string;
};