Class vs Structure in Swift
🏛 Class vs Structure in Swift: Key Differences and When to Use Each
In Swift, both classes and structures (structs) are essential building blocks for defining custom data types. While they may appear similar, they serve different purposes due to their unique characteristics. In this blog, we’ll explore their key differences and guide you on when to use a class versus a struct.
Key Differences Between Class and Struct
Understanding the differences between classes and structs is crucial for choosing the right tool for your project. Let’s break them down:
1. Reference vs. Value Types
- Classes are reference types, meaning that when you pass or assign a class instance, you are sharing a reference to the same object. Any changes made to one instance affect all references to that object.
- Structs are value types. When you pass or assign a struct, you are creating a copy. Changes to the copy do not affect the original instance.
2. Inheritance
- Classes support inheritance, allowing one class to inherit properties and behaviors from another.
- Structs do not support inheritance. They are designed to be lightweight and lack the complexities of class hierarchies.
3. Mutability
- Classes allow property values to be changed even if the instance is declared with
let, as long as the properties themselves are mutable. - Structs declared with
letare immutable. All properties become read-only, preventing any modifications to the struct’s properties.
4. Deinitializers
- Classes can have deinitializers, which are special methods that get called when an instance is deallocated.
- Structs cannot have deinitializers because they are automatically deallocated when they go out of scope.
5. Identity and Equality
- Classes are compared by reference, meaning that two instances are considered equal only if they point to the same memory address.
- Structs are compared by value, meaning that two instances are considered equal if all their properties are identical.
When to Use a Class
Classes are most appropriate when you need reference semantics, shared state, or inheritance. Here are a few situations where classes are ideal:
1. Shared State Across Instances
If you need shared data across multiple parts of your app, use a class. For instance, a network manager might be shared across different view controllers, and changes to its state should be reflected throughout the app.
2. Inheritance and Polymorphism
When you need one entity to inherit behavior or properties from another, classes are the go-to solution. For example, in a view hierarchy where you have multiple types of views (e.g., UILabel, UIButton), inheritance allows you to share common functionality across these views.
3. Managing Large, Complex Objects
When handling complex objects that you don’t want to duplicate across memory, such as a data model with many properties, classes prevent unnecessary copying, which helps with performance in larger applications.
4. When You Need Deinitialization
If you need to release resources like file handles or network connections when an object is deallocated, use a class, as it allows for a deinitializer to clean up resources.
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