how to normalize with redux tool and creactentityAdapter - redux

Question

i using redux tool kit to build react native app and i try to normalize my data like this
const postEntitiy = new schema.Entity('post');
const postAdapter = createEntityAdapter({
selectId: (post) => post._id,
});
const normalized = normalize(response.data, postEntitiy);
this is my resopose.data
Array [
Object {
"__v": 5,
"_id": "6020b367cb94a91c9cd48c34",
"comments": Array [],
"date": "2021-02-08T03:43:35.742Z",
"likes": Array [
Object {
"_id": "60216bd341b3744ce4b13bee",
"user": "601f2d46017c85357800da96",
},
],",
},
]
and this is the error it throw
The entity passed to the `selectId` implementation returned undefined., You should probably provide
your own selectId implementation.,
The entity that was passed:, Object {
"undefined": Object {
"0": Object {
"__v": 5,
"_id": "6020b367cb94a91c9cd48c34",
"comments": Array [],
"date": "2021-02-08T03:43:35.742Z",
"likes": Array [
Object {
"_id": "60216bd341b3744ce4b13bee",
"user": "601f2d46017c85357800da96",
},
],
},
]

Answer 1

As this is written the postAdapter and the normalize are independent of each other. What's happening here is that normalize is attempting the map the data into entities, but it ends up with the key as undefined because it is using the default key of id which has an undefined value. Additionally you have an array of entities rather than just one.
The postAdapter then tries to find the selectId on this data which has already been normalized. But the postAdapter is not looking at a single post object -- it is looking at the nested data created by normalize. It is looking at the data structure Object { "undefined": Object { "0": Object {... from your error. The "undefined": is caused by the bad id attribute and the "0": is because it is an array.
How you do write this correctly kind of depends on what it is that you are trying to do. It's possible that normalize is not really necessary here. It looks like the likes in response.data are already returning a string id for the like and the user instead of the deeply-nested data that the normalizr package is designed to flatten. If you want to use normalize and have it work properly then you need to set the idAttribute on the options argument (docs link).
const postEntity = new schema.Entity('post', {}, {idAttribute: '_id'});
const normalized = data.map( o => normalize(o, postEntity));
idAttribute also accepts a function. You can create a reusable id extractor function that pulls the _id property from any object with {_id: string;}.
const myIdExtractor = (object : {_id: string;}) => object._id;
const postEntity = new schema.Entity('post', {}, {idAttribute: myIdExtractor});
const normalized = data.map( o => normalize(o, postEntity));
That same id extractor function also works with createEntityAdapter.
const postAdapter = createEntityAdapter({
selectId: myIdExtractor,
});