Plain old model structures. These models do not have any logic and only consist of properties. There are four types of model:

• TodoRequest: This is a struct that is used in backend request calls and conforms to RequestProtocol
• Todo: This is a struct that represents Todo data, and uses the Argo and Curry libraries to decode the object from JSON
• TodoViewModel and TodosViewModel: These structs represent data and are used in views and shown to the user
• TodoLens: These lenses modify the Todo model

All the aforementioned models are immutable value types.