41ViewModell

41ViewModell is a software architectural approach described as a variant of the Model-View-ViewModel (MVVM) pattern. It is used in application development to structure UI code around a central ViewModel that exposes state and actions to the View, while the Model holds domain data and rules. The term appears in a range of German-language tutorials and smaller open-source projects, but it lacks a formal, universally recognized specification. As such, its exact practices can vary between teams.

Core idea: to maximize testability and maintainability by keeping business logic in the ViewModel and minimizing logic within the View. The View remains a passive renderer that binds to observable properties, and a binding or mediation layer synchronizes changes between View and ViewModel. The Model remains the source of truth for domain data.

Typical components: Model (domain data and rules), ViewModel (state, derived properties, commands), View (UI and binding targets), and a binding layer or framework.

Common patterns: unidirectional data flow, explicit command handling, dependency injection for test doubles, and declarative bindings. Platform support ranges from desktop to mobile to web, with implementations often utilizing existing data-binding facilities.

Benefits: improved testability, clearer separation of concerns, and easier state management in complex UIs. Limitations: added boilerplate, potential learning curve, and risk of over-architecting simple interfaces.

See also: MVVM, data binding, Model-View-Controller, Model-View-Presenter.