What is the difference between MVVM and MVC in iOS?

Both MVVM and MVC are software architectural patterns used to organize the code of iOS applications. Their differences are as follows:

The MVC (Model-View-Controller) pattern is one of the most common architectural patterns in iOS development. In MVC, the application is divided into three main components:

1. Model: Responsible for handling data logic and business logic, typically serving as the data source for the application.
2. View: Responsible for displaying data and the user interface, typically the user interface portion of an application.
3. Controller: responsible for coordinating the interaction between the Model and View, as well as handling user input and application logic.

MVVM (Model-View-ViewModel) is an evolved version based on MVC. In MVVM, the application is divided into three main components: Model, View, and ViewModel.

1. Model: Similar to the model in MVC, it is responsible for handling data logic and business logic.
2. View: Similar to the view in MVC, responsible for displaying data and user interface.
3. ViewModel: In the MVVM pattern, a ViewModel is introduced to adapt model data into the necessary format for the view, as well as handle user input and application logic. The ViewModel can also achieve two-way binding with the View through data binding mechanisms, allowing changes in data to automatically reflect on the view.

Therefore, compared to MVC, MVVM has an additional ViewModel layer, which helps decouple the View and Model by introducing the ViewModel and providing a data binding mechanism. This simplifies the synchronization of views and model data, making the code clearer and more maintainable, while also enhancing testability.