以下代码在Swift 1.2中编译:
class myClass {
static func myMethod1() {
}
class func myMethod2() {
}
static var myVar1 = ""
}
func doSomething() {
myClass.myMethod1()
myClass.myMethod2()
myClass.myVar1 = "abc"
}
静态函数和类函数的区别是什么?我应该用哪一个，什么时候用?
如果我尝试定义另一个变量类var myVar2 = ""，它会说:
类中还不支持类存储属性;你是说“静电”吗?
当支持此特性时，静态变量和类变量之间的区别是什么(即当两者都在类中定义时)?我应该用哪一个，什么时候用?
(Xcode 6.3)
当前回答
我在操场上尝试了米帕迪的回答和评论。我想分享它。给你。我认为米帕迪的回答应该被认可。
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(){
}
//Let's 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(){
}
}
其他回答
Static和class都将方法与类关联，而不是类的实例。区别在于子类可以重写类方法;它们不能覆盖静态方法。
类属性以同样的方式起作用(子类可以重写它们)。
我在操场上尝试了米帕迪的回答和评论。我想分享它。给你。我认为米帕迪的回答应该被认可。
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(){
}
//Let's 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(){
}
}
还有一个区别:类只能用于定义计算类型的类型属性。如果需要存储类型属性，请使用static。
使用static关键字定义类型属性。对于类类型的计算类型属性，可以使用class关键字来允许子类重写超类的实现。 https://docs.swift.org/swift-book/LanguageGuide/Properties.html
Swift类vs静态类
[参考与值类型]
class在引用类型(类，函数)中使用:
计算属性 方法 可以被子类覆盖吗
static用于引用类型(类，函数)和值类型(结构体，enum，元组):
计算属性和存储属性 方法 不能通过子类更改
protocol MyProtocol {
// class var protocolClassVariable : Int { get }//ERROR: Class properties are only allowed within classes
static var protocolStaticVariable : Int { get }
// class func protocolClassFunc()//ERROR: Class methods are only allowed within classes
static func protocolStaticFunc()
}
struct ValueTypeStruct: MyProtocol {
//MyProtocol implementation begin
static var protocolStaticVariable: Int = 1
static func protocolStaticFunc() {
}
//MyProtocol implementation end
// class var classVariable = "classVariable"//ERROR: Class properties are only allowed within classes
static var staticVariable = "staticVariable"
// class func classFunc() {} //ERROR: Class methods are only allowed within classes
static func staticFunc() {}
}
class ReferenceTypeClass: MyProtocol {
//MyProtocol implementation begin
static var protocolStaticVariable: Int = 2
static func protocolStaticFunc() {
}
//MyProtocol implementation end
var variable = "variable"
// class var classStoredPropertyVariable = "classVariable"//ERROR: Class stored properties not supported in classes
class var classComputedPropertyVariable: Int {
get {
return 1
}
}
static var staticStoredPropertyVariable = "staticVariable"
static var staticComputedPropertyVariable: Int {
get {
return 1
}
}
class func classFunc() {}
static func staticFunc() {}
}
final class FinalSubReferenceTypeClass: ReferenceTypeClass {
override class var classComputedPropertyVariable: Int {
get {
return 2
}
}
override class func classFunc() {}
}
//class SubFinalSubReferenceTypeClass: FinalSubReferenceTypeClass {}// ERROR: Inheritance from a final class
关于面向对象编程，答案太简单了:
子类可以重写类方法，但不能重写静态方法。
除了你的帖子，如果你想声明一个类变量(就像你做的class var myVar2 = "")，你应该这样做:
class var myVar2: String {
return "whatever you want"
}
