filter.md

Filter

1 What Does a Filter Do?

Filter is a function that is run "before", "after" a controller action.

It have the same parameter ability as the controller action.

2 Usage

"before" filters may halt the request cycle. A common "before" filter is one which requires that a user is logged in for an action to run.

@Filter()
class AuthenticateFilter implements IMiddleware {

  public use(@Res() res: Express.Response, @Next() next: Express.NextFunction) {
    if (// use is logged in) {
      next();
    } else {
      res.sendStatus(403);
    }
  }
}

@RestController()
@BeforeFilter(AuthenticateFilter)
class AuthenticatedResourceController {}

The AuthenticateFilter checks if the user is logged in or not. If user haven't logged in, then response with forbidden.

The AuthenticatedResourceController decorated with AuthenticateFilter, that means every route/action inside this controller will run after filter. If you want some actions can run for anonymous user, you need specify the exception case for filter

// Filter definition

@RestController()
@BeforeFilter(AuthenticateFilter, {only: ['indexAction']})
// Or @BeforeFilter(AuthenticateFilter, {except: ['indexAction']})
class AuthenticatedResourceController {}

As an example, the only options in the filter means only indexAction will run after filter in this controller, while the except options means except indexAction, others all run after filter.

In a filter, it is important to call next() to continue the call chains and request to the next Filter or Controller.

3 Data

You can pass data between different Controller, Filter, Middleware use decorator @Data.

@Filter()
class FindUserFilter implements IMiddleware {

  public use(@Data() data: any, @Next() next: Express.NextFunction) {
    data.user = # findById();
    next();
  }
}

@RestController()
@BeforeFilter(FindUserFilter)
class PostController {

  public(@Data() data: any, @Res() res: Express.Response) {
    typeof data.user !== 'undefined' # => true
  }
}

In this example, FindUserFilter save user information with decorator @Data, then controller can use data.user directly.