Unlocking the Power of Swift: Classes and Structs Demystified
When it comes to building flexible and efficient programs in Swift, understanding the differences between classes and structs is crucial. These fundamental building blocks allow developers to store data and model behavior in their code, but what sets them apart?
The Similarities: Interchangeability and Flexibility
Both classes and structs can define properties to store values, providing different options for storing data and modeling behavior. They share similar features, including:
- Initializers that set up initial state values using the
init()keyword - The ability to define subscripts, providing quick access to a sequence’s value, collection, or list
- The ability to extend a class or struct using the
extensionkeyword - Protocol conformance
The Differences: Classes Take Center Stage
While structs and classes share similarities, classes have additional capabilities that set them apart. Classes can inherit all properties, behaviors, and methods from another class, as well as add extra capabilities to what’s inherited. Type casting also enables developers to check and interpret a class instance type at runtime.
Syntax Similarities: Defining Classes and Structs
The syntax for defining classes and structs in Swift is similar. To define a class or struct, use the class or struct keyword followed by the name of the class or struct with curly braces. Ensure that class and struct names follow the PascalCase naming convention.
Class Definitions: Providing Default Values and Initializers
In Swift, every class must have an initializer. If a class has subclasses, the initializer assures the compiler that the subclasses inherit or implement the same initializer. This enables us to define class definitions with default values or custom initializers.
Struct Definitions: Creating Immutable Values
Structs, on the other hand, are defined differently. They are value types, and any changes made to a variable assigned to a struct’s instance affect the original struct, making its value immutable.
Creating Class Instances: Objects and Mutability
Swift class instances are known as objects and are mutable. Because classes are reference types, any changes made to a variable assigned to a class instance affect the original class, making it mutable.
Accessing Properties and Methods
To access a class’s data, use the dot notation. You can also use the dot notation syntax to set values to variable properties, allowing you to add additional data. Both classes and structs can define methods to provide functionality using the func keyword.
Class Inheritance: A Fundamental Feature
Inheritance is a fundamental feature in classes that differentiates them from structs. Understanding how inheritance works is important when deciding whether to use a class or struct. Subclassing allows us to inherit from one class to another, meaning a class (designated as a subclass) accesses all data from another class (designated as a superclass).
Values and References: The Key Difference
A fundamental feature that sets structs and classes apart is that structs are value types and classes are reference types. When creating a struct and assigning it to a variable, the value is copied because it is a value type. However, when classes are assigned to a variable, it references the existing instance rather than copying it.
When to Use Classes vs. Structs in Swift
The official Apple documentation recommends using structs by default, especially in multithreaded environments. However, classes are preferable when:
- Class inheritance is needed
- You need to control an object’s identity
- You’re working with complex data values
Conclusion
Classes and structs provide flexibility when working in Swift. While they share similarities, their slightly different capabilities provide developers the choices they need. By understanding the differences between classes and structs, you can make informed decisions about which to use in your code.