Mini is a minimal Flux architecture written in Kotlin that also adds a mix of useful features to build UIs fast.

You should use this library if you aim to develop a reactive application with good performance (no reflection using code-gen). Feature development using Mini is fast compared to traditional architectures (like CLEAN or MVP), low boilerplate and state based models make feature integration and bugfixing easy as well as removing several families of problems like concurrency or view consistency across screens.

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//Dispatch an action on the main thread synchronously
dispatcher.dispatch(LoginAction(username = "user", password = "123"))

//Post an event that will dispatch the action on the UI thread and return immediately.
dispatcher.dispatchAsync(LoginAction(username = "user", password = "123"))

The Stores are holders for application state and state mutation logic. In order to do so they expose pure reducer functions that are later invoked by the dispatcher.

The state is plain object (usually a data class) that holds all information needed to display the view. State should always be inmutable. State classes should avoid using framework elements (View, Camera, Cursor...) in order to facilitate testing.

Stores subscribe to actions to change the application state after a dispatch. Mini generates the code that links dispatcher actions and stores using the @Reducer annotation over a non-private function that receives an Action as parameter.

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Each Store exposes a custom StoreCallback though the method observe or a Flowable if you wanna make use of RxJava. Both of them emits changes produced on their states, allowing the view to listen reactive the state changes. Being able to update the UI according to the new Store state.

  //Using RxJava  
  userStore
          .flowable()
          .map { it.name }
          .subscribe { updateUserName(it) }
          
  // Custom callback      
  userStore
          .observe { state -> updateUserName(state.name) }

If you make use of the RxJava methods, you can make use of the SubscriptionTracker interface to keep track of the Disposables used on your activities and fragments.

A Task is a basic object to represent an ongoing process. They should be used in the state of our Store to represent ongoing processes that must be represented in the UI. Having the next code:

data class LoginAction(val username: String, val password: String)
data class LoginCompleteAction(val loginTask: Task, val user: User?)

data class SessionState(val loginTask: Task = taskIdle(), val loggedUser: User? = null)

class SessionStore @Inject constructor(val controller: SessionController) : Store<SessionState>() {
    @Reducer
    fun login(action: LoginAction): SessionState {
        controller.login(action.username, action.password)
        return state.copy(loginTask = taskRunning(), loggedUser = null)
    }

    @Reducer
    fun loginComplete(action: LoginCompleteAction): SessionState {
        return state.copy(loginTask = action.loginTask, loggedUser = action.user)
    }
}

The workflow will be:

• View dispatch LoginAction.
• Store changes his LoginTask status to running and call though his SessionController which will do all the async work to log in the given user.
• View shows an Spinner when LoginTask is in running state.
• The async call ends and LoginCompleteAction is dispatched on UI, sending a null User and an error state Task if the async work failed or a success Task and an User.
• The Store changes his state to the given values from LoginCompleteAction.
• The View redirect to the HomeActivity if the task was success or shows an error if not.

Mini includes some utility extensions over RxJava 2.0 to make easier listen state changes over the Stores.

• mapNotNull: Will emit only not null values over the given map clause.
• select: Like mapNotNull but avoiding repeated values.
• onNextTerminalState: Used to map a Task inside an state and listen the next terminal state(Success - Error). Executing a different closure depending of the result of the task.

To avoid loops over when working with navigation based on a process result. You will need to make use of onNextTerminalState after dispatch and Action that starts a process which result could navigate to a different screen. For example:

  fun login(username: String, password: String) {
        dispatcher.dispatch(LoginAction(username, password))
        sessionStore.flowable()
                .onNextTerminalState(taskMapFn = { it.loginTask },
                        successFn = { navigateToLogin() },
                        failureFn = { showError(it) })
    }

If we continually listen the changes of a Task and we navigate to a specific screen when the Task becomes successful. The state will stay on SUCCESS and if we navigate back to the last screen we will be redirected again.

Mini includes a custom LoggerInterceptor to log any change in your Store states produced from an Action. This will allow you to keep track of your actions, changes and side-effects more easily. To add the LoggerInterceptor to your application you just need to add a single instance of it to your Dispatcher after initialize it in your Application class or dependency injection code.

val loggerInterceptor = CustomLoggerInterceptor(stores().values)
dispatcher.addInterceptor(loggerInterceptor)

Mini includes an extra library called mini-android-testing with a few methods and Expresso TestRules to simplify your UI tests over this architecture.

• TestDispatcherRule : This rule will intercept any action that arrives to the Dispatcher, avoiding any call to the Store and their controllers. If we include this rule we will need to change the states manually in our tests.
• CleanStateRule : It just reset the state of your stores before and after each test.

Example of test checking that an action is correctly dispatched:

@get:Rule
val testDispatcher = testDispatcherRule()

@Test
fun login_button_dispatch_login_action() {
    onView(withId(R.id.username_edit_text)).perform(typeText("someUsername"))
    onView(withId(R.id.password_edit_text)).perform(typeText("somePassword"))
    onView(withId(R.id.login_button)).perform(click())
    
    assertThat(testDispatcher.actions, contains(LoginAction(someUsername, somePassword)))
}

Example of test checking that a view correctly changes with an specify state:

@get:Rule
val cleanState = cleanStateRule()

@Test
fun login_redirects_to_home_with_success_task() {
     //Set login state to success
     onUiSync {
         val loggedUser = User(email = MockModels.anyEmail, uid = MockModels.anyId, username = MockModels.anyUsername, photoUrl = MockModels.anyPhoto)
         val state = SessionState().copy(loginRequestState = requestSuccess(), verified = false, loggedIn = true, loggedUser = loggedUser)
         sessionStore.setTestState(state)
     }
     //Redirect to Email verification activity
     intended(hasComponent(HomeActivity::class.java.name))
}

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