In Swift, the decision to use classes over structs depends on several key factors related to the nature of the data and the behavior you need to model. Here are the primary considerations for when to use classes instead of structs:
1. Reference Semantics
Classes are reference types, meaning that when you assign or pass around an instance of a class, you are working with references to the same instance. This is useful when you need multiple parts of your code to share and modify the same instance of an object. In contrast, structs are value types and are copied when assigned or passed around, which means each copy is independent of the others[1][3][7].
2. Inheritance
Classes support inheritance, allowing you to create a hierarchy of classes that share properties and methods. This is essential when you need to create a base class with common functionality that can be extended by subclasses. Structs do not support inheritance, so if your design requires a type hierarchy, you must use classes[1][3][5][7].
3. Identity
If you need to maintain the identity of an object, use a class. Each instance of a class has a unique identity, which is important in scenarios where the identity of the object itself matters, such as managing the state of a user interface component or a network connection[2][4][7].
4. Deinitialization
Classes can have deinitializers (deinit), which are called when an instance of the class is deallocated. This is useful for cleaning up resources, such as closing file handles or network connections. Structs do not have deinitializers[5][9].
5. Shared Mutable State
When you need to manage shared mutable state, classes are the appropriate choice. Since classes are reference types, changes made to an instance in one part of your code will be reflected in all references to that instance. This is particularly useful in scenarios where you need to ensure consistency across different parts of your application[2][4][7].
6. Objective-C Interoperability
If you need to interact with Objective-C APIs or frameworks, you should use classes. Classes in Swift can be marked with the @objc attribute to expose them to the Objective-C runtime, which is necessary for interoperability with many Apple frameworks[2][3].
7. Complex Data Models
For complex data models that require behavior and state management, classes are often more suitable. Classes can encapsulate more complex behavior and can be extended through inheritance, making them a better fit for more intricate data structures[5][7].
Summary
In summary, you should use classes over structs in Swift when you need reference semantics, inheritance, identity...
