Is there a way to get the tag of a polymorphic variant as a variable in ReasonML

Question

I'm looking to see if i can genericize the following code a bit.

type recordType = [
  | `Todo(todo, idFunction)
  | `TodoItem(todoItem, idFunction)


let commitItemToSchema = (normalizedSchema, recordType) => {
  switch(recordType){
  | `Todo    (todo,     idFun) => {...normalizedSchema, todo:       addOrModifyById(normalizedSchema.todo,       todo,       idFun)}
  | `TodoItem(todoItem, idFun) => {...normalizedSchema, todoItem:   addOrModifyById(normalizedSchema.todoItem,   todoItem,   idFun)}
  };
};

Is there a way that I can get the \'Todo or the 'TodoItem from the variant as a variable?

Thanks

Can you provide the types of everything shown in the code sample? — Yawar, Apr 26 '18 at 22:48

score 0 · Answer 1 · answered May 10 '18 at 06:18

It would be helpful if you showed us the complete set of types. OCaml/BuckleScript/ReasonML do support polymorphic types. Here is simple type and value declaration using a polymorphic type in ReasonML.

type wrapper('a) = {
  item: 'a,
  details: string
};

let x = {item: 1, details: "This is an int"};

Here are two kinds of functions that take a wrapper with an unrestricted type 'a and a wrapper with a restricted type 'a as int.

let unrestrictedType = (x: wrapper('a)) => {
  Js.log(x);
};

let restrictedType = (x: wrapper(int)) => {
  Js.log(x);
};

score -1 · Answer 2 · answered Jun 13 '18 at 20:28

-1

If the variant could be passed as variable, it would lose type check in that case. I don't think ReasonML support that.

answered Jun 13 '18 at 20:28

Yan

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Is there a way to get the tag of a polymorphic variant as a variable in ReasonML

2 Answers2