Static vs class functions/variables in Swift classes?

i0S Swift Issue

Question or problem with Swift language programming:

The following code compiles in Swift 1.2:

class myClass {
    static func myMethod1() {
    class func myMethod2() {
    static var myVar1 = ""

func doSomething() {
    myClass.myVar1 = "abc"

What is the difference between a static function and a class function? Which one should I use, and when?

If I try to define another variable class var myVar2 = “”, it says:

When this feature is supported, what will the difference be between a static variable and a class variable (i.e. when both are defined in a class)? Which one should I use, and when?

(Xcode 6.3)

How to solve the problem:

Solution 1:

static and class both associate a method with a class, rather than an instance of a class. The difference is that subclasses can override class methods; they cannot override static methods.

class properties will theoretically function in the same way (subclasses can override them), but they’re not possible in Swift yet.

Solution 2:

I tried mipadi’s answer and comments on playground. And thought of sharing it. Here you go. I think mipadi’s answer should be mark as accepted.

class A{
    class func classFunction(){
    static func staticFunction(){
    class func classFunctionToBeMakeFinalInImmediateSubclass(){

class B: A {
    override class func classFunction(){


    //Compile Error. Class method overrides a 'final' class method
    override static func staticFunction(){


    //Lets avoid the function called 'classFunctionToBeMakeFinalInImmediateSubclass' being overriden by subclasses

    /* First way of doing it
    override static func classFunctionToBeMakeFinalInImmediateSubclass(){

    // Second way of doing the same
    override final class func classFunctionToBeMakeFinalInImmediateSubclass(){

    //To use static or final class is choice of style.
    //As mipadi suggests I would use. static at super class. and final class to cut off further overrides by a subclass

class C: B{
    //Compile Error. Class method overrides a 'final' class method
    override static func classFunctionToBeMakeFinalInImmediateSubclass(){


Solution 3:

Regarding to OOP, the answer is too simple:

The subclasses can override class methods, but cannot override static methods.

In addition to your post, if you want to declare a class variable (like you did class var myVar2 = ""), you should do it as follow:

class var myVar2: String {
    return "whatever you want"

Solution 4:

Testing in Swift 4 shows performance difference in simulator. I made a class with “class func” and struct with “static func” and ran them in test.

static func is:

  • 20% faster without compiler optimization
  • 38% faster when optimization -whole-module-optimization is enabled.

However, running the same code on iPhone 7 under iOS 10.3 shows exactly the same performance.

Here is sample project in Swift 4 for Xcode 9 if you like to test yourself

Solution 5:

I got this confusion in one of my project as well and found this post, very helpful. Tried the same in my playground and here is the summary. Hope this helps someone with stored properties and functions of type static, final,class, overriding class vars etc.

class Simple {

    init() {print("init method called in base")}

    class func one() {print("class - one()")}

    class func two() {print("class - two()")}

    static func staticOne() {print("staticOne()")}

    static func staticTwo() {print("staticTwo()")}

    final func yesFinal() {print("yesFinal()")}

    static var myStaticVar = "static var in base"

    //Class stored properties not yet supported in classes; did you mean 'static'?
    class var myClassVar1 = "class var1"

    //This works fine
    class var myClassVar: String {
       return "class var in base"

class SubSimple: Simple {
    //Successful override
    override class func one() {
        print("subClass - one()")
    //Successful override
    override class func two () {
        print("subClass - two()")

    //Error: Class method overrides a 'final' class method
    override static func staticOne() {


    //error: Instance method overrides a 'final' instance method
    override final func yesFinal() {


    //Works fine
    override class var myClassVar: String {
        return "class var in subclass"

And here is the testing samples:


class - one()
class - two()
init method called in base
subClass - one()
static var in base
class var in base
class var in subclass

Hope this helps!