Guards

A guard is a class annotated with the @Injectable() decorator, which implements the CanActivate interface.

Guards have a single responsibility. They determine whether a given request will be handled by the message handler or not, depending on certain conditions (like permissions, roles, ACLs, etc.) present at run-time.

Author guard

1@Injectable()
2export class IsAuthorGuard implements CanActivate {
3  canActivate(
4    msg: proto.IWebMessageInfo, 
5    socket: WASocket
6  ): boolean | Promise<boolean> {
7    return msg.key.fromMe;
8  }
9}

Every guard must implement a canActivate() function. This function should return a boolean, indicating whether the current message handler is allowed or not. It can return the response either synchronously or asynchronously (via a Promise). Fastwa uses the return value to control the next action:

• if it returns true, the message will be processed.
• if it returns false, Fastwa will deny the message.

Binding guards

Guards are method-scoped. Below is an example of a method-scoped guard using the @UseGuards() decorator. This decorator may take a single argument, or a commma-separated list of arguments. This lets you easily apply the appropriate set of guards with one declaration.

1@Command('ping')
2@UseGuards(IsAuthorGuard)
3ping() {
4  return this.appService.getPing();
5}

Good to know: The @UseGuards() decorator is imported from @fastwa/common package.