How describe model for Record<string, string> TS type?

[KyryloSWAN]

I have the following data for which I need to create a model:

{
  "some": [
    {"a": "b"},
    {"c": "d"},
    {"e": "f"}
  ]
}

The key of object in array item can be any string.
I can use Array<Record<string, string>> to describe my data as TypeScript type.
But I can't figure out how I can describe the mst model for my data.

[coolsoftwaretyler]

Hey @KyryloSWAN - here's how I might model this out to start

const TopLevelObject = types
  .model("TopLevelObject", {
    some: types.array(types.frozen),
  });

It seems like the keys in each of your records are dynamic, and might not be suitable for "typing" in advance. In this case, the frozen type allows you to work with these objects, since they're serializable.

I do this from time to time when it comes with new third party APIs, where I'm not yet sure what data I'm going to really want or need to model out from them. We sometimes store JSON blobs as frozen types, until we can determine a better way to model the data that we expect to use from it.

[KyryloSWAN]

Thank you, @coolsoftwaretyler!
frozen works!

[KyryloSWAN]

I'm trying to use types.frozen<Record<string, string>>() to decribe model for Array<Record<string, string>> | undefined type:

export const ProfileStore = types
  .model({
    autoExchangeDestinations: types.maybe(
      types.array(types.frozen<Record<string, string>>())
    ),
})
  .actions((self) => {
    return {
      getUserProfileById: flow(function* getUserProfile(id: string) {
...
          self.autoExchangeDestinations =
                    fetchedArray === null
                      ? undefined
                      : [...fetchedArray];
        }
      }),
    };
  });

where fetchedArray has Record<string, string>[] | null type.
And got error TS2322:

error TS2322: Type 'Record<string, string>[] | undefined' is not assignable to type '(IMSTArray<IType<Record<string, string>, Record<string, string>, Record<string, string>>> & IStateTreeNode<IMaybe<IArrayType<IType<Record<string, string>, Record<...>, Record<...>>>>>) | undefined'.
  Type 'Record<string, string>[]' is not assignable to type 'IMSTArray<IType<Record<string, string>, Record<string, string>, Record<string, string>>> & IStateTreeNode<IMaybe<IArrayType<IType<Record<string, string>, Record<...>, Record<...>>>>>'.
    Type 'Record<string, string>[]' is missing the following properties from type 'IMSTArray<IType<Record<string, string>, Record<string, string>, Record<string, string>>>': spliceWithArray, clear, replace, remove, toJSON

114                   self.autoExchangeDestinations =
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

What I'm doing wrong?

[coolsoftwaretyler]

Ah yes, that looks like a known problem with TS, MST, and arrays. Try the solution listed here: #957 (comment)

Let me know if that helps or not.

[KyryloSWAN]

It helps!

                  self.autoExchangeDestinations =
                    autoExchangeDestinations === null
                      ? undefined
                      : cast([...autoExchangeDestinations]);

works with flying colors!
Thank you for your help @coolsoftwaretyler