@ngrx/entity add mapOne method

[awonihlgard]

Similiar to setOne and updateOne, it would be useful with a mapOne for cases where you want to update a single entity but the new value depends on the old. Example:

return adapter.mapOne(id, entity => {
    ...entity,
    counter: entity.counter + 1
}, state);

The naming of map would then be a bit inconsistent, but that might be fine. For full consistency the naming would mapOne and mapAll (mapMany could also be added for completeness).

Describe any alternatives/workarounds you're currently using

The same thing can be accomplished by accessing the old entity with state.entities, but it becomes a bit more verbose if you also want to check for existence:

const entity = state.entities[id];
if (entity) {
    return state.updateOne({
        id,
        changes: {
            counter: entity.counter + 1
        }
    })
} else {
    return state;
}

If accepted, I would be willing to submit a PR for this feature

[x] Yes (Assistance is provided if you need help submitting a pull request)
[ ] No

[timdeschryver]

What about using the map method for it, it looks as follows:

const withUpdates = adapter.map(
      entity =>
        entity.id === action.id
          ? { ...entity, counter: entity.counter +1 }
          : entity,
      state
    );

[kbrilla]

@timdeschryver This is not performant when a lot of entities exist. The updateOne approach is better, but I can see how the proposed mapOne approach results in a much cleaner approach, and fit well with other adapter methods.

[awonihlgard]

Yes, the performance concern is why I gave updateOne as an alternative. Even if using map is fine in most cases it feels inelegant to iterate every entity when you only want to update one.

[timdeschryver]

IIRC this is not the first time that this feature came up to discussion.
What do you think about adding this to @ngrx/entity @brandonroberts, if @awonihlgard wants to create a PR for it?

If we want to forward with this, how would it behave if no entity is found for the key? Should it just ignore it, or invoke the map with an undefined entity?

[kbrilla]

I would say It should pass without an error and no change should be made to state. Also, should update methods start to check that entity is provided with different id than the one passed as an argument? W dniu wt., 16.06.2020 o 13:01 Tim Deschryver <notifications@github.com> napisał(a):

…

IIRC this is not the first time that this feature came up to discussion. What do you think about adding this to @ngrx/entity @brandonroberts <https://github.com/brandonroberts>, if @awonihlgard <https://github.com/awonihlgard> wants to create a PR for it? If we want to forward with this, how would it behave if no entity is found for the key? Should it just ignore it, or invoke the map with an undefined entity? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#2538 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFKBQQP372NHZRMYTKDJKT3RW5GIJANCNFSM4NHZES7Q> .