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

class static swift
Jean-Philippe Pellet picture Jean-Philippe Pellet · Aug 6, 2014 · Viewed 101.1k times · Source

I can see these definitions in the Swift library:

extension Bool : BooleanLiteralConvertible {
    static func convertFromBooleanLiteral(value: Bool) -> Bool
}

protocol BooleanLiteralConvertible {
    typealias BooleanLiteralType
    class func convertFromBooleanLiteral(value: BooleanLiteralType) -> Self
}

What's the difference between a member function defined as static func and another one defined as class func? Is it simply that static is for static functions of structs and enums, and class for classes and protocols? Are there any other differences that one should know about? What is the rationale for having this distinction in the syntax itself?

Answer

Jake Lin picture Jake Lin · Mar 3, 2016

To be clearer, I make an example here,

class ClassA {
  class func func1() -> String {
    return "func1"
  }

  static func func2() -> String {
    return "func2"
  }

  /* same as above
  final class func func2() -> String {
    return "func2"
  }
  */
}

static func is same as final class func

Because it is final, we can not override it in subclass as below:

class ClassB : ClassA {
  override class func func1() -> String {
    return "func1 in ClassB"
  }

  // ERROR: Class method overrides a 'final` class method
  override static func func2() -> String {
    return "func2 in ClassB"
  }
}

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