Structs vs Classes

Relax. We'll talk through this in plain words — no textbook voice.

In Swift, the two go-to tools for building custom data models are struct and class. A struct is a value type, so copying it creates a brand-new piece of data. A class is a reference type, so copying it usually just means both references point to the same single object.

For app models and simple data containers, it's a good idea to reach for struct first. Use class when you need shared mutable state or inheritance.

swift

struct Course {
    var title: String
    var lessonCount: Int
}

class Student {
    var name: String
    var enrolledCourse: Course?

    init(name: String) {
        self.name = name
    }
}

let swiftCourse = Course(title: "Swift Basics", lessonCount: 20)
let student = Student(name: "Nandar")
student.enrolledCourse = swiftCourse

print(student.name)
print(student.enrolledCourse?.title ?? "No course")

Course is a simple data model, so it's written as a struct. Student has an initializer and is written as a class so a course can be linked to it later. enrolledCourse? is optional because a course might not have been chosen yet.

You should see

Nandar Swift Basics

Easy traps

If you don't give a class property an initial value and don't set it in the initializer either, you'll get a compile error.