What is MVVM?
MVVM stands for Model-View-ViewModel. It’s a design pattern that separates an app’s data (Model), its user interface (View), and the logic that connects the two (ViewModel) so each part can be built and tested independently.
Let's break it down
- Model: the raw data and business rules, like a list of products or a calculation engine.
- View: what the user actually sees on the screen - buttons, text, images, etc.
- ViewModel: a middle-man that takes data from the Model, prepares it for the View, and sends user actions back to the Model. It “binds” the View and Model together without them talking directly.
Why does it matter?
Because it keeps code organized, makes it easier to change one part without breaking others, and allows developers and designers to work side-by-side. This leads to faster development, fewer bugs, and apps that are easier to maintain.
Where is it used?
- Desktop applications built with WPF (Windows Presentation Foundation) or UWP on Windows.
- Mobile apps using Xamarin.Forms or .NET MAUI for iOS and Android.
- Web front-ends that employ frameworks like Knockout.js or Vue.js which follow MVVM-like concepts.
- Game UI layers in Unity where UI logic is separated from game data.
Good things about it
- Clear separation of concerns makes code more readable and testable.
- Enables two-way data binding, so UI updates automatically when data changes.
- Facilitates parallel work: designers can craft the View while developers focus on Model and ViewModel.
- Improves reusability: the same ViewModel can serve multiple Views (e.g., phone and tablet layouts).
- Simplifies unit testing because business logic lives outside the UI.
Not-so-good things
- Can introduce extra boilerplate and complexity for very small or simple apps.
- Two-way binding may hide performance issues if not managed carefully.
- Learning curve: beginners must grasp three separate components and their interactions.
- Over-engineering risk: applying MVVM where a simpler pattern would suffice can waste time.