F# WPF MVVM can I do this without making the view model variables mutable?

Question

I'm learning F#, I want to build the next module of my home project. So far most of my F# code has been test code written with the command line. I also did some custom drawing to a Winforms Panel. So far, I haven't had to use one mutable variable. but now I'm trying to write some actual code and as soon as I got to the ViewModel part it seemed that I had no choice but to make the variables that will interact with the UI mutable. Is this true, or is there something I'm missing?

Answer 1

For MVVM, F# carries one very significant advantage: it does not allow circular dependencies. This makes it very difficult to break the pattern: i.e. to allow the model to directly affect the viewmodel, or the viewmodel to access the view. As Bent says, F# is multi-paradigm: it supports properties with getters and setters, and these are not things to be eschewed in the language.

It's interesting that I'm citing a lack of capability as one of the advantages of F#, but I feel it is precisely this preclusion of circular dependencies that makes the language a good choice for an enterprise architecture.

I have a toy project at https://github.com/SpiegelSoft/Astrid. You can look through that to see how I've implemented MVVM using ReactiveUI.