Grappa

Decorator-powered REST client for Angular 9+ and its HttpClient, plus RxJs 6+.

For previous versions of Angular use Grappa v0.6.0.

Installation

With npm:

$ npm i --save @elemental-concept/grappa

With Yarn:

$ yarn add @elemental-concept/grappa

Add GrappaModule to your main AppModule to imports section.

@NgModule({
  declarations: [ ... ],
  imports: [
    ...,
    GrappaModule
  ],
  providers: [ ],
  bootstrap: [ ... ]
})
export class AppModule { }

Introduction

Grappa minimises boiler-plate code required for REST clients and streamlines request and response modifications with filters. Simply define a list of methods which reflect REST API:

@Injectable()
@RestClient('http://example.com/api/')
export class UserService {
  @GET('/users')
  list: () => Observable<User[]>;

  @GET('/users/{0}')
  find: (id: number) => Observable<User>;

  @POST('/users')
  create: (user: User) => Observable<User>;

  @PUT('/users/{0}')
  update: (id: number, user: User) => Observable<User>;
}

Grappa will auto-generate required class methods which can be easily called from any component:

@Component({
  // ...
})
export class AppComponent {
  constructor(private userService: UserService) {
    userService.find(42).subscribe(user => console.log(user));
  }
}

Define @BeforeRequest() filter methods to uniformly modify data being sent to the API. A good example could be JWT injection, but we are covering that with a separate library Grappa JWT

Custom header injection is a good example:

@Injectable()
@RestClient('http://example.com/api/')
export class UserService {
  // ...

  constructor(private authService: AuthService) {}

  @BeforeRequest()
  private customHeaders(request: RestRequest) {
    request.headers = {
      ...request.headers,
      'X-Xid': id,
      'X-Client-Id': clientId,
      'X-User-Id': userId,
    };
  }
}

Use @AfterRequest() to transform responses and inject global error handlers:

@Injectable()
@RestClient('http://example.com/api/')
export class UserService {
  // ...

  @AfterRequest()
  tranformResponse(response: Observable<HttpResponse<any>>) {
    return response.map(item => User.fromResponse(item.body));
  }

  @AfterRequest()
  handleErrors(response: Observable<HttpResponse<any>>) {
    return response.catch(error => {
      alert('Error!');
      return Observable.of(error);
    });
  }
}

API

Decorators on a class and its properties define how a request will be handled.

`@RestClient(baseUrl: string = '')`

Optional decorator which allows to define base URL for all REST methods in a class. If decorator is not present or baseUrl argument is empty string, null or undefined, then it is assumed that property decorators will contain full URLs.

Example with @RestClient:

@Injectable()
@RestClient('http://example.com/api/')
export class UserService {
  @GET('/users')
  list: () => Observable<User[]>; // List method will call http://example.com/api/users
}

Example without @RestClient:

@Injectable()
export class UserService {
  @GET('http://somedomain.org/users')
  list: () => Observable<User[]>; // List method will call http://somedomain.org/users
}

`@GET(endpoint: string, options: RequestOptions = {})`

Makes HTTP GET request to the specified end-point. Arguments passed to the decorated function can be inserted into end-point URL using index based templates. Indices start at 0. Example:

@GET('/users/{0}/posts?page={1}')
getUserPosts: (userId: number, page: number) => Observable<Post[]>;

{0} will be replaced with userId value and {1} will be replaced with page value.

`@POST(endpoint: string, options: RequestOptions = {})`

Makes HTTP POST request to the specified end-point. Arguments passed to the decorated function can be inserted into end-point URL using index based templates. Indices start at 0. Last function argument will be used as a POST body.

@POST('/users')
create: (user: User) => Observable<User>;

`@PUT(endpoint: string, options: RequestOptions = {})`

Makes HTTP PUT request to the specified end-point. Arguments passed to the decorated function can be inserted into end-point URL using index based templates. Indices start at 0. Last function argument will be used as a PUT body.

@PUT('/users/{0}', options: RequestOptions = {})
update: (userId: number. user: User) => Observable<User>;

`@DELETE(endpoint: string, options: RequestOptions = {})`

Makes HTTP DELETE request to the specified end-point. Arguments passed to the decorated function can be inserted into end-point URL using index based templates. Indices start at 0. Example:

@DELETE('/users/{0}')
remove: (userId: number) => Observable<User>;

`@BeforeRequest(applyTo: OptionalList<string> = null)`

Runs decorated method before every request in a class.

@BeforeRequest()
beforeFilter(request: RestRequest) {
  request.headers[ 'X-Dummy' ] = 'Abcde';
}

`@AfterRequest(applyTo: OptionalList<string> = null)`

Runs decorated method after every request in a class.

@AfterRequest()
afterFilter(response: Observable<HttpResponse<any>>) {
  return response.map(r => r.body.value);
}

RequestOptions

Configuration for specific GET, POST, PUT and DELETE requests.

export interface RequestOptions {
  observe?: ObserveOptions;
  query?: number | boolean;
  emptyBody?: boolean;
}

export enum ObserveOptions {
  Body = 'body',
  Response = 'response'
}

Given

@GET('/users/{0}/posts?page={1}')
getUserPosts: (userId: number, page: number) => Observable<Post[]>;

you'll have {1} as the page attribute, but if instead you have multiple query params, the best approach is to have a single object and then use the query option:

@GET('/users/{0}/posts', { query: true })
getUserPosts: (userId: number, { page: number, search: string, sort: string, hideOutOfStock: boolean }) => Observable<Post[]>;

This way Grappa will translate the object into a list of query params, like this:

`/users/{0}/posts?page=${page}&search=${search}&sort=${sort}&hideOutOfStock=${hideOutOfStock}`

If for any reason you need to send a PUT or a POST without a body (which is not a good practise), we added a new flag emptyBody, that allow that. So you could send something like this:

@PUT('/users/{0}', { emptyBody: true })
getUserPosts: (userId) => Observable<Post[]>;

OptionalList

Allows to specify the names of request methods specific filter should apply.

export type OptionalList<T> = T | T[] | null;

Usage:

@GET('/users')
get: () => Observable<User[]>;

@POST('/users')
create: (user: User) => Observable<User>;

@BeforeRequest('create')
beforeFilter(request: RestRequest) {
  // This filter function will only apply to create() calls
}

kohoward / grappa