Can you explain me the difference static and class in swift?

Question

Can you show me when and why I should use keyword static and when I should use keyword class? (This is Type Property Syntax in Swift)

Answer 1

The difference between a function defined as static func and another one defined as class func is that static is for functions of structures and enumerations, and class is mainly for functions of protocols and classes.

Class functions can also be overridden by subclasses. For example:

class Animal{
    class func generateAnimalSound(){
        print("Some Animal Sound")
    }
    static func isAnimal() -> Bool{
        return true
    }
}

class Cat: Animal{
    override class func generateAnimalSound(){
        print("Meow!")
    }
}

var someAnimal = Animal.generateAnimalSound()  // prints "Some Animal Sound"
var cat = Cat.generateAnimalSound()  // prints "Meow!"

However, if you try to override the static member function isAnimal(), this will result in an error:

Cannot override static method

That's obviously because static methods cannot be overridden by subclasses. You should read the documentation provided both by Apple and other StackOverflow related questions:

• What is the difference between static func and class func in Swift?

• static vs class as class variable/method (Swift)

• The Swift Programming Language (Swift 3.1) - Methods

Answer 2

You should check the Guides written by Apple on "The Swift Programming Language". The page about Classes and Structures is relevant for you. Read them and understand the examples. Then you will know when to use structs and when not.

This useful excerpt should answer your question: The Swift Programming Language - Classes and Structures

Comparing Classes and Structures

Classes and structures in Swift have many things in common. Both can:

• Define properties to store values
• Define methods to provide functionality
• Define subscripts to provide access to their values using subscript syntax
• Define initializers to set up their initial state
• Be extended to expand their functionality beyond a default implementation
• Conform to protocols to provide standard functionality of a certain kind

Classes have additional capabilities that structures do not:

• Inheritance enables one class to inherit the characteristics of another.
• Type casting enables you to check and interpret the type of a class instance at runtime.
• Deinitializers enable an instance of a class to free up any resources it has assigned.
• Reference counting allows more than one reference to a class instance.

NOTE: Structures are always copied when they are passed around in your code, and do not use reference counting.