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Working with route models
We often use routes’ models throughout our application, since they’re a core ingredient of our application’s data. As such, we want to make sure that we have good types for them!
We can start by defining some type utilities to let us get the resolved value returned by a route’s model hook:
import Route from '@ember/routing/route';
/**
Get the resolved type of an item.
- If the item is a promise, the result will be the resolved value type
- If the item is not a promise, the result will just be the type of the item
*/
export type Resolved<P> = P extends Promise<infer T> ? T : P;
/** Get the resolved model value from a route. */
export type ModelFrom<R extends Route> = Resolved<ReturnType<R['model']>>;
How that works:
Resolved<P>
says "if this is a promise, the type here is whatever the promise resolves to; otherwise, it's just the value"ReturnType<T>
gets the return value of a given functionR['model']
(whereR
has to beRoute
itself or a subclass) uses TS's mapped types to say "the property namedmodel
onR
Putting those all together,
ModelFrom<Route>
ends up giving you the resolved value returned from the model
hook for a given route:type MyRouteModel = ModelFrom<MyRoute>;
We can use this functionality to guarantee that the
model
on a Controller
is always exactly the type returned by Route::model
by writing something like this:import Controller from '@ember/controller';
import MyRoute from '../routes/my-route';
import { ModelFrom } from '../lib/type-utils';
export default class ControllerWithModel extends Controller {
declare model: ModelFrom<MyRoute>;
}
Now, our controller’s
model
property will always stay in sync with the corresponding route’s model hook.Note: this only works if you do not mutate the
model
in either the afterModel
or setupController
hooks on the route! That's generally considered to be a bad practice anyway. If you do change the type there, you'll need to define the type in some other way and make sure your route's model is defined another way.Last modified 2yr ago