Cayla  Erdman

Cayla Erdman


Fabulous: Functional App Development | Xamarin Blog

his is a guest blog by Timothé Larivière. Timothé is the maintainer of Fabulous and a Microsoft MVP. You can find him on Twitter @Tim_Lariviere.

Fabulous App Development

Fabulous is an open-source framework for building mobile & desktop apps using functional programming (FP) with F#, a .NET functional-first programming language. It is available on GitHub at

Applications built with Fabulous use the MVU design pattern (Model-View-Update, also known from the origin The Elm Architecture). These app also use declarative views written directly in F#.

This may already feel familiar to you if you have played with frameworks like React-Redux, Flutter, or SwiftUI.

Object-oriented programming (OOP) is widely used today. However, in this post, we will elaborate on how FP can also be an awesome tool for building apps.

_A few apps made with Fabulous for Xamarin.Forms, from left to right: FabulousWeatherFabulousContacts and _FabulousPlanets

Image FabulousWeatherImage FabulousContacts

Fundamentals of MVU

Note: We will see MVU as defined by Elm, which is the definition used by many F## libraries.

The upcoming MAUI will integrate a different variant of it.

Before diving in, let’s expand on what the MVU pattern is and how it differs from more traditional MVVM apps.

Image of MVU

Credits: Beginning Elm (

The idea is to have a state (also called Model) that is immutable and can only be changed through messages (Msg) that are processed by the update function. Those messages are then sent when users interact with the application or when external factors happen. Such as async request completes, push notifications, and switching between dark and light modes. Each time the state is updated, Fabulous will ask for the matching UI state and will transition between them transparently.

MVU provides several advantages over MVVM:

  • Immutable state

In MVVM, the ViewModel (which holds the state) is mutable and is usually changed in multiple methods in reaction to what happens. When the app grows bigger, make extra effort and be careful when adding new changes to not break existing behaviors unknowingly. In MVU, the immutability of the app state ensures that it won’t ever be changed outside of the dedicated update function, without a dedicated message. This makes it very simple to add new features without worrying about breaking something.

  • Centralization & explicitness
  • The structure of MVU is really simple and enforces explicitness.
  • The state can only be initialized in the init function and changed in the update function only for declared Msgs, the UI can only be declared in the view function.
  • This makes it really easy to welcome new developers to the codebase and makes debugging a lot easier.
  • If it breaks, there’s only one place.
  • No concurrency issues
  • The user navigates, data gets loaded, animations end, … Reacting to one event is easy, but when you need to handle multiple events at the same time, it becomes tricky.
  • This can lead to obscur errors, very hard to understand and sometimes impossible to reproduce.
  • Fabulous helps you avoid this kind of problem by applying concurrent messages one after the other.
  • Also, Fabulous lets you monitor its MVU loop so you can know what happened in which order.
  • Easy to replay that one corner case!
  • Ease of testing
  • A best practice in FP is to write functions that only depend on their parameters and not on the global context, much like static methods.
  • Those functions are called pure and are really easy to test, for the same parameters you’ll always get the exact same output.
  • With MVU, the initupdate and view functions are pure by default. Meaning you can unit test them super easily, including your UI!
  • You can see an example here.

#developers #xamarin.forms #app development #f# #fabulous #mobile applications #mobile apps #mvu

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Fabulous: Functional App Development | Xamarin Blog
Fredy  Larson

Fredy Larson


How long does it take to develop/build an app?

With more of us using smartphones, the popularity of mobile applications has exploded. In the digital era, the number of people looking for products and services online is growing rapidly. Smartphone owners look for mobile applications that give them quick access to companies’ products and services. As a result, mobile apps provide customers with a lot of benefits in just one device.

Likewise, companies use mobile apps to increase customer loyalty and improve their services. Mobile Developers are in high demand as companies use apps not only to create brand awareness but also to gather information. For that reason, mobile apps are used as tools to collect valuable data from customers to help companies improve their offer.

There are many types of mobile applications, each with its own advantages. For example, native apps perform better, while web apps don’t need to be customized for the platform or operating system (OS). Likewise, hybrid apps provide users with comfortable user experience. However, you may be wondering how long it takes to develop an app.

To give you an idea of how long the app development process takes, here’s a short guide.

App Idea & Research


_Average time spent: two to five weeks _

This is the initial stage and a crucial step in setting the project in the right direction. In this stage, you brainstorm ideas and select the best one. Apart from that, you’ll need to do some research to see if your idea is viable. Remember that coming up with an idea is easy; the hard part is to make it a reality.

All your ideas may seem viable, but you still have to run some tests to keep it as real as possible. For that reason, when Web Developers are building a web app, they analyze the available ideas to see which one is the best match for the targeted audience.

Targeting the right audience is crucial when you are developing an app. It saves time when shaping the app in the right direction as you have a clear set of objectives. Likewise, analyzing how the app affects the market is essential. During the research process, App Developers must gather information about potential competitors and threats. This helps the app owners develop strategies to tackle difficulties that come up after the launch.

The research process can take several weeks, but it determines how successful your app can be. For that reason, you must take your time to know all the weaknesses and strengths of the competitors, possible app strategies, and targeted audience.

The outcomes of this stage are app prototypes and the minimum feasible product.

#android app #frontend #ios app #minimum viable product (mvp) #mobile app development #web development #android app development #app development #app development for ios and android #app development process #ios and android app development #ios app development #stages in app development

Rahim Makhani

Rahim Makhani


Get your own Mobile App with the latest Xamarin app development service

Xamarin is the best fit for mobile app developers who work on cross-platform applications such as various languages for coding and UI paradigms. It also allows developers to use C# for Android, iOS, and Windows apps.

Xamarin app development services are the latest app development services. Xamarin is built on an open-source platform built-in .Net framework. It is used for mobile app development. Xamarin is a cross-platform implementation of the common language infrastructure and common language specification.

Nevina Infotech will help you to develop your own mobile app with Xamarin app development services. We have the best mobile app developers who will help you to develop your mobile app.

#xamarin app development #xamarin development company #xamarin application development services #xamarin mobile app development #xamarin app development services #xamarin mobile development

React Native vs Xamarin: What to choose for cross-platform app development?

React Native vs Xamarin: What to choose for cross-platform app development? With most brands focussing on cross-platform app development, it is of extreme importance to ensure that app development takes place on the right kind of platform. According to Statista, by the year 2020, mobile apps are predicted to generate $581.9 billion in global revenue via paid downloads and in-app advertising. With multiple options available in the market, we explore two popular ones: Xamarin App Development and React Native and help you to choose the best one for you.

Original Source :

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