Smart Signals

And now, we can use the ChildDefinitionSignals interface to create a "selector" that will retrieve the child entity for the parent entity. We can use this selector in our components to retrieve the row(s) and their children from the store.

Note that the createSmartSignal function takes an array of ChildDefinitionSignals objects. This allows us to create a signal that will retrieve multiple child entities from the parent entity. That is, one row may point to multiple children. By passing the array you can account for each of them with one call.

In the case where your User row might have some child field named, roles your createSmartSignal call might look like this:

export const selectUserChildren = createSmartSignal(selectUser, [
  {
    childFeature: 'shared',
    childEntity: 'roles',
    parentField: 'roles',
    parentFeature: 'shared',
    parentEntity: 'users',
    childSelector: selectRoles,
  },
]);

The first parameter to createSmartSignal expects a signal that returns the parent entity. If you want to use some other selector, you'll need to convert it to a signal that returns an Entity first.

In order for smartSignals to work correctly, there are two conditions.

First, all the signals used in a SmartSignal must also be SmartSignals. If you need a signal that has no children, you can retrieve it by using the feature name and entity name:

const rawSignal = createSmartSignal('feature', 'entity);

Secondly, signals need to be chained. That is, if you have an entity that has children that itself has children, each childSelector must point to the smart signal that retrieves the entities children.