Swift Language Guide - Type Properties and Methods

• Type properties and methods are like static in Java.
• Use static in Value Type and class in Reference Type
• Type computed property and methods can NOT use instance member data.

Type Properties

• Stored and Computed property belong to Value type (Structure and Enumerations)
• Reference Type (Class) only has Computed property
• Stored Type Property MUST have initial value.

Syntax

• Enumerations

    enum TestEnum {
        static var staticX = 0
  
        static var staticY : Int {
            get {
            return staticX + 10
            }
            set {
                staticX = newValue - 10
            }
        }
    }
  
    println(TestEnum.staticX)
    println(TestEnum.staticY)
    TestEnum.staticY = 30
    println(TestEnum.staticX)
  

• Structure

    struct TestStruct {
        static var staticX = 0
  
        static var staticY : Int {
            get {
            return staticX + 10
            }
            set {
                staticX = newValue - 10
            }
        }
    }
  
    println(TestStruct.staticX)
    println(TestStruct.staticY)
    TestStruct.staticY = 50
    println(TestStruct.staticX)
  

• Class

    var globalX = 0
    class TestClass {
        class var classX : Int {
            get {
                return globalX + 10
            }
            set {
                globalX = newValue - 10
            }
        }
    }
  
    println(TestClass.classX)
    TestClass.classX = 90
    println(TestClass.classX)
    println(globalX)
  

Type Methods

• Do NOT need 'mutating` when type method of value type changing type property.

• Enumerations

    enum TestEnum {
        static var staticX = 0
  
        static var staticY : Int {
            get {
            return staticX + 10
            }
            set {
                staticX = newValue - 10
            }
        }
  
        static func addStaticY(y: Int) {
            staticY = y
        }
    }
  
    println(TestEnum.staticX)
    println(TestEnum.staticY)
    TestEnum.addStaticY(30)
    println(TestEnum.staticX)
  

• Structure

    struct TestStruct {
        static var staticX = 0
  
        static var staticY : Int {
            get {
            return staticX + 10
            }
            set {
                staticX = newValue - 10
            }
        }
  
        static func addStaticY(y: Int) {
            staticY = y
        }
    }
  
    println(TestStruct.staticX)
    println(TestStruct.staticY)
    TestStruct.addStaticY(50)
    println(TestStruct.staticX)
  

• Class

    var globalX = 0
    class TestClass {
        class var classX : Int {
            get {
                return globalX + 10
            }
            set {
                globalX = newValue - 10
            }
        }
  
        class func addClassX(x: Int) {
            classX = x
        }
    }
  
    println(TestClass.classX)
    TestClass.addClassX(90)
    println(TestClass.classX)
    println(globalX)