Update single amplify model field with custom GraphQL mutation in Flutter

Question

I am trying to update single field in Amplify model using GraphQL in Flutter.
As far as I know Amplify.API.mutate and Amplify.DataStore.save can only update entire models.

In the doc in subset-of-data section there is an example how to run custom query to get object.
I tried to analogically write mutation but cannot get it done.

 const graphQLDocument = '''mutation update {
  updateUserData(input:
    {
      id: "123",
      name: "John"
    }) {
    email
  }
}''';

Then request:

final updateUserName = GraphQLRequest<UserData>(
  document: graphQLDocument,
  modelType: UserData.classType,
  decodePath: getTodo, /**/
);

final response = await Amplify.API.mutate(request: updateUserGoal).response;

I am not sure what is decodePath in this case?
If I don't pass it I get "message": "No decodePath found",.

Or maybe I should use GraphQLOperation instead of GraphQLRequest?

Answer 1

The decodePath you can generate from standard mutation:

UserData model = UserData(id: '123');
final mutation = ModelMutations.update(model);

Then use it:

decodePath: mutation.decodePath

I still have problem with authorization so I am not sure if that's a correct way to do it. Happy to hear about any suggestions.