Reducto is a port of Redux to .NET

What is Reducto?

Reducto is a keeper of the state for your app. It helps to organize the logic that changes that state. Really useful for GUI apps in combination with(but not limited to) MVVM, MVC, MVP etc.

Metric	Value
lines of code	~260
dependencies	0
packaging	NuGet PCL

Installation

In Package Manager Console run

PM> Install-Package Reducto

Key concepts

• Action - an object which describes what has happened - LoggedIn, SignedOut, etc. The object contains all the information relevant to the action - username, password, status, etc. Usually there are many actions in an app.
• Reducer - a side-effect free function that receives the current state of your app and an action. If the reducer does not know how to handle the action it should return the state as is. If the reducer can handle the action it 1.) makes a copy of the state 2.) it modifies it in response to the action and 3.) returns the copy.
• Store - it is an object that contains your app's state. It also has a reducer. We dispatch an action to the store which hands it to the reducer together with the current app state and then uses the return value of the reducer as the new state of the app. There is only one store in your app. It's created when your app starts and gets destroyed when your app quits. Your MVVM view models can subscribe to be notified when the state changes so they can update themselves accordingly.
• Async action - a function that may have side effects. This is where you talk to your database, call a web service, navigate to a view model, etc. Async actions can also dispatch actions (as described above). To execute an async action it needs to be dispatched to the store.
• Middleware - these are functions that can be hooked in the store dispatch mechanism so you can do things like logging, profiling, authorization, etc. It's sort of a plugin mechanism which can be quite useful.

Dispatching an action to the store is the only way to change its state.
Dispatching an async action cannot change the state but it can dispatch actions which in turn can change the state.

How does one use this thing?

Here is a short example of Reducto in action. Let's write an app that authenticates a user.

First, let's define the actions that we will need:

// Actions

public struct LoginStarted 
{ 
    public string Username; 
}

public struct LoginFailed {}

public struct LoginSucceeded 
{
    public string Token;
}

Next is the state of our app

// State

public enum LoginStatus 
{
    LoginInProgress, LoggedIn, NotLoggedIn
}

public struct AppState
{
    public LoginStatus Status;
    public String Username;
    public String Token;
}

Here is how the actions change the state of the app

var reducer = new SimpleReducer<AppState>()
    .When<LoginStarted>((state, action) => {
        state.Username = action.Username;
        state.Token = "";
        state.Status = LoginStatus.LoginInProgress;
        return state;
    })
    .When<LoginSucceeded>((state, action) => {
        state.Token = action.Token;
        state.Status = LoginStatus.LoggedIn;
        return state;
    })
    .When<LoginFailed>((state, action) => {
        state.Status = LoginStatus.NotLoggedIn;
        return state;
    });

var store = new Store<AppState>(reducer);

Now let's take a moment to see what is going on here. We made a reducer using a builder and define how each action changes the state. This reducer is provieded to the store so the store can use it whenever an action is dispatched to it. Makes sense so far? I hope so ;)

Now let's see what is dispatching actions to the store. One can do that directly but more often then not it will be done from inside an async action like this one

var loginAsyncAction = store.asyncAction(async(dispatch, getState) => {
    dispatch(new LoginStarted{Username = "John Doe"});

    // faking authentication of user
    await Task.Delay(500);
    var authenticated = new Random().Next() % 2 == 0;

    if (authenticated) {
        dispatch(new LoginSucceeded{Token = "1234"});
    } else {
        dispatch(new LoginFailed());
    }
    return  authenticated;
});

A lot going on here. The async action gets a dispatch and a getState delegates. The latter one is not used in our case but the former is used a lot. We dispatch an action to signal the login process has started and then again after it has finished and depending on the outcome of the operation. How do we use this async action?

store.Dispatch(loginAsyncAction);
// or if you need to know the result of the login you can do also
var logged = await store.Dispatch(loginAsyncAction);

For more examples and please checkout the links below in the Resources section

Resources

A couple of links on my blog

• Better MVVM with Xamarin Forms
• Compartmentalizing logic

What about the name?

It is pure magic ;-)