Angular SWR

Data fetching for Angular 14+

Usage

Create a service that fetches data

const endpoint = "https://jsonplaceholder.typicode.com/todos"

@Injectable({ providedIn: "root" })
export class Fetcher implements Fetchable<Todo[]> {
   private http = inject(HttpClient)
   
   fetch(userId: string) {
      return this.http.get(endpoint, { params: { userId }})
   }
}

Create a resource

import { createResource, revalidateOnFocus, refreshInterval, revalidateOnReconnect } from "@mmuscat/angular-swr"

export const TODOS = createResource(Fetcher, {
   features: [
      revalidateOnFocus,
      revalidateOnReconnect,
      refreshInterval(60_000)
   ]
})

Provide and use resource in component

import { TODOS } from "./resource"

@Component({
   selector: "app-todos",
   templateUrl: "./todos.component.html",
   providers: [TODOS],
})
export class TodosComponent {
   protected todos = inject(TODOS)
   
   @Input()
   userId: string
   
   ngOnChanges() {
      this.todos.fetch(this.userId)
   }
}

Read values in template

<!-- todos.component.html -->
<div *ngIf="todos.error">
   Something went wrong
   <button (click)="todos.revalidate()">Retry</button>
</div>
<spinner *ngIf="todos.pending"></spinner>
<todo *ngFor="let todo of todos.value" [value]="todo"></todo>

Options

export interface ResourceOptions {
   providedIn?: Type<any> | "root" | "platform" | "any" | null
   immutable?: boolean
   timeoutMs?: number
   dedupeMs?: number
   cache?: boolean
   refetchIfStale?: boolean
   serialize?: (...params: any[]) => string
   features?: ResourceFeatureWithOptions<{}>[]
}

property	default	description
providedIn	null	Configure which module the resource is provided in
immutable	false	Prevent refetching a resource that is already cached with the given params
timeoutMs	3000	How long a resource should wait after fetching without receiving a response before it is marked as slow
dedupeMs	2000	How long a resource should wait before allowing a duplicate fetch with the same params
cache	true	Disables caching when set to false, useful when fetch is used to send data
revalidateIfStale	true	Control whether a resource should revalidate when mounted if there is stale data
serialize	JSON.stringify	Serializer used to stringify fetch parameters
features	void	A list of ResourceFeatureWithOptions that add additional behaviours to the resource

Adding Features

Resource behavior can be customised by adding features.

revalidateOnFocus

Revalidate a resource every time the current page receives window focus.

revalidateOnReconnect

Revalidate a resource every time the network connection comes back online.

refreshInterval

Revalidate a resource periodically according to a timer.

Writing Custom Features

Create a class that implements the ResourceFeature interface.

interface ResourceFeature<T extends {}> {
   onInit?(resource: Resource, options: T): void
   onConnect?(resource: Resource, options: T): void
   onDisconnect?(resource: Resource, options: T): void
   onDestroy?(resource: Resource, options: T): void
}

Example

import { createFeature, Fetchable, Resource, ResourceFeature } from "@mmuscat/angular-swr"

interface LoggerOptions {
   token?: Type<{ log: (resource: Resource) => void }>
}

@Injectable({ providedIn: "root" })
export class Logger implements ResourceFeature<LoggerOptions> {
   private injector = inject(INJECTOR)

   onInit(resource: Resource<T>, { token }: LoggerOptions) {
      const logger = this.injector.get(token, console)
      resource.subscribe(() => {
         logger.log(resource)
      })
   }
}

export function logger(token: Type<any>) {
   return createFeature(Logger, { token })
}

Usage

@Injectable({ providedIn: "root" })
class MyLogger {
   log(resource: Resource) {
      // log implementation
   }
}

const RESOURCE = createResource(Fetcher, {
   features: [
      logger(MyLogger)
   ]
})