Type, that fallbacks null | undefined to []

[haalogen]

How to make a type, that fallbacks null | undefined to [] ?
Smth like types.optional(Type, []), but which thinks null is also an empty value

[EmilTholin]

Hi @haalogen!

types.optional has a third optional argument optionalValues that you can use to specify what values you want to override with the defaultValue.

Example

import { types } from "mobx-state-tree";

const Type = types.array(types.string);

const OtherType = types.model({
  type: types.optional(Type, [], [undefined, null])
});

const otherType = OtherType.create({
  type: null
});

console.log(otherType.type); // []