Mastering the Model Layer: Iron-Clad State Management in Model-Driven Apps

Model-driven architectures like MVVM and MVC have been pivotal in iOS development, but challenges arise when scaling to complex applications, particularly with state management. SwiftUI has shifted focus towards the Model View approach, but developers often struggle with maintaining the state when dealing with external events. The article emphasizes promoting state as the core of an application, distinguishing it from the Model layer, which is often burdened with responsibilities like network handling. It uses the Munchee app as an example to showcase state management strategies, highlighting the importance of defining state structures, understanding their lifecycle, and ensuring state transitions are valid according to business rules. The article advises against incorporating screen-specific rules into the state and instead suggests using ViewModels to transform data for UI presentation. It warns against creating a "god class" by overloading the state with responsibilities and recommends handling navigation and ephemeral states separately to maintain a clean and scalable architecture. The approach ensures a unidirectional flow of events and reduces dependencies between ViewModels, facilitating easier scaling and testing.