In this article, we will learn about classes and Structs, the Difference between classes and structs and common features.

Class

Classes are reference types. It means that if you assign an instance of the class to a variable, it will hold only the reference to the instance and not the copy.

class Person { var name: String init(name: String) { self.name = name } }

var ceo = SomeClass(name: “steve”) var newCeo = ceo //ceo and newCeo now reference the same instance! newCeo.name = “Tim”

println(ceo.name) // “Tim” println(newCeo.name) // “Tim”

Struct

Structs are value types. It means that if you copy the instance of the structure to another variable, it’s just copied to the variable.

struct Person { var name: String init(name: String) { self.name = name } }

var ceo = Person(name: “Steve”) var newCeo = ceo //ceo and newCeo are two structs with the same value! newCeo.name = “Tim”

println(ceo.name) // “Steve” println(newCeo.name) // “Tim”

Common features between classes and structs

  • Define properties to store values
  • Define methods to provide functionality
  • Can be extended using the extensions (very powerful)
  • Can conform to protocols (protocol orientation)
  • Define initializers
  • Define Subscripts to provide access to their variables
  • They can work with generics to provide flexible and reusable types

Difference between classes and structs

  • A class supports Type casting but struct doesn’t.
  • A class can have deinitializer as its a reference type but a struct doesn’t as it is a value type.
  • A class supports Inheritance but a struct doesn’t.
  • A class allows reference counting for multiple references but a struct doesn’t.
  • Struct properties are stored on Stack and Class instances are stored on Heap memory
  • Struct is thread safe or singleton at any point in time.

FAQ

Q1. Can structs have retain cycle? 

ans: No, more info

Q2. Can structs be weak? 

ans: No, As structs are value type they can’t be weak, strong or unowned