Build mobile apps with Xamarin and F#
Xamarin is well known as a platform for building cross-platform mobile apps using C#, but did you know it also supports F#? This leads to a conundrum - C# development is very object-oriented so how can you use F# to build mobile apps but retain the function programming paradigms that make F# such a powerful language? Recently a new language and architecture called Elm appeared in the javascript community with a structure based on immutable models and functions to create and update the UI. This maps really well to functional languages and similar architectures are popping up in the F# community under the banner of ‘Elmish’ - first for web apps using Fable and more recently for Xamarin.Forms apps using Elmish.XamarinForms. Watch the presentation here: https://www.youtube.com/watch?v=si9YdWhbwSI
Recommended
Recommended
More Related Content
Recently uploaded
Recently uploaded (20)
Featured
Featured (20)
Build mobile apps with Xamarin and F#
- 11. @jimbobbennett
- 14. @jimbobbennett
Editor's Notes
- Build cross-platform apps with immutable models and UI with a lot less code using F#, Xamarin.Forms and Elmish This presentation looks at building Xamarin apps in F# In particular, using Xamarin.Forms with Elmish.XamarinForms to provide immutable models and UI
- F# foundation - body that manages F# It is a mature language – came out of Microsoft Research. First stable release was 2005 Open source – managed by the F# foundation with oversight/primary development from Microsoft Can’t be truly independent because of links to .NET Because it is a .NET language it has full interop with everything .NET, so it supports OO code
- Functional programming is not scary Seems so due to lots of academia with long words like lambda calculus, monads (which as everyone knows are monoids in the category of endofunctors) It’s actually an easy to use language, partly because you can get away with writing very little code
- As F# is a .NET language it runs wherever C# runs VS2017 and Mac have full support So does VSCode thanks to the Ionide extension Can use it for anything C# can do Azure Functions support F# For more functional style, tools like Fable for Web
- F# works – just drop in a replacement for C# Demo
- Based on the MVU pattern – model, view, update Came from Elm in the Javascript world Each app has a model type and some defined messages. A init method creates a model An update method is called with messages – from UI or other services Update returns a new model, copying the old one and adjusting New model is passed to view which returns a representation of the UI Framework updates the real UI based off the representation
- Simple example – incrementing a model
- The elm pattern always has an immutable model and synchronised update, so no threading issues One model is the single source of truth, so no managing state in different models and view models UI representation isn’t a real UI, so can be fully unit tested without running the app The view function doesn’t interact with the UI, so can be run off the UI thread to reduce UI load
- F# has Elmish – like Elm Originally used with Fable for web Elmish.XamarinForms brings this to Xamarin Forms 2 variants – half and full
- Half elmish – ideal for Xamarin developers who are used to MVVM/binding and want to try out F# Model and update are in code View returns bindings UI is XAML, bound to the results of the view function Can’t unit test the UI, just the bindings
- Full elmish – all in, F# only, no XAML View function returns ‘shadow’ UI Framework looks for differences between shadow UI and real UI and updates UI to match
- F# works – just drop in a replacement for C# Demo
- This framework is reasonably stable, but still in beta Third party controls are not supported in full elmish The XAML namespace will change – not sure what to yet More needs to be done on the navigation stacks, documentation… Please get involved
- To get started Docs Samples, Awesome elmish Dotnet new Get in touch