Middleware

Middleware serves as a tool to intercept navigation between screens under specific conditions. For instance, when a user attempts to navigate to a screen that requires authentication, but the user is not signed in, the Middleware intercepts the navigation and redirects the user to the sign-in screen.

Middleware is created in two steps:

1. Create a Middleware Annotation

   First, create a middleware annotation and mark it with the @Middleware annotation:

@Middleware
annotation class MiddlewareSample

2. Create a Middleware Controller

   Next, create a Middleware controller by inheriting from MiddlewareController or MiddlewareControllerComponent. Mark it with the previously created annotation to connect this controller to the annotation:

@MiddlewareSample
class MiddlewareControllerSample: MiddlewareController

From this point, you can use your annotation to mark a RouteController, indicating that it should call this middleware before navigating to the controller's screen.

@Route
@MiddlewareSample
abstract class SampleRouteController: RouteControllerApp<SamplePath, SampleScreen>()

The difference between MiddlewareController and MiddlewareControllerComponent is that the latter includes the onInject method. This method is called after the middleware is created and provides the instance of the component for injection.

@MiddlewareSample
class MiddlewareControllerSample: MiddlewareController
{
    // Implement necessary methods here 
}

@MiddlewareSample
class MiddlewareControllerComponentSample: MiddlewareControllerComponent
{
    override fun onInject(component: Any)
    {
        // Implement injection logic here 
    }
}

Full code example:

// Create middleware annotation
@Middleware
annotation class MiddlewareAuth

// Mark MiddlewareController as MiddlewareAuth
@MiddlewareAuth
class MiddlewareControllerAuth: MiddlewareControllerComponent
{
    @Inject
    lateinit var userData: UserData

    // This will be called for injection
    override fun onInject(component: Any)
    {
        (component as AppComponent).inject(this)
    }

    // This method will be called during navigation
    override fun onRoute(router: Router, prev: RoutePath?, next: RouteParamsGen): Boolean
    {
        if (!userData.isLogin.value!!)
        {
            router.route(AuthPath(next))
            return true // return true to block the current navigation 
        }

        return false
    }
}

// Then mark the RouteController as MiddlewareAuth 
@Route
@MiddlewareAuth
abstract class TabAuthRouteController: RouteControllerApp<TabPath2, TabViewModel, TabFragment>()