标签：tiger color eats eat 学习 var legs Swift Class
1.声明Class
class A{
var str = "Hello, Class"
var number = 1
}
//创建类的实例
var a = A()
print(a.str)
//打印结果：Hello, Class
2.类与结构体不同，类没有默认初始化方法。我们需要在类内部自己定义初始化方法传参。
结构体可以直接写为：
var a = A(str:"test",number:10)
但是用同样方法写类的时候是会报错的，如果不自定义初始化方法，只能使用空初始化:
var a = A()
自定义初始化方法
class B{
var str = "Hello, Class"
var number = 1
init(str: String,number: Int){
self.str = str
self.number = number
}
//无参初始化，委托初始化方法
// convenience init(){
// self.init(str: "Hello, Class",number: 1)
// }
//或者这样定义也可以
init() {
str = "Declare as many initalisers as you want"
number = 0
}
}
var b = B(str: "Hello this is B", number: 2)
print("Default String is \(b.str) and Default number is \(b.number)")
//打印结果：Default String is Hello this is B and Default number is 2
如果自定义了初始化方法，此时申明空初始化会报错；
提示：Missing arguments for parameters 'str', 'number' in call
此时，我们可以在类中声明一个代理依托，声明一个无参初始化。此时就不报错了。
3.类继承：类支持继承，结构体不支持
子类继承父类的特征，然后可以对其进行优化，并添加新的特征
class Animal{
var isVeg : Bool
var eats : String
var numberOfLegs : Int
init(isVeg: Bool, eats: String, numberOfLegs: Int) {
self.isVeg = isVeg
self.eats = eats
self.numberOfLegs = numberOfLegs
}
func printProperties(){
print("Is Veg? \(isVeg). Eats:\(eats). Number of legs:\(numberOfLegs)")
}
}
var anim = Animal(isVeg: false, eats: "Can eat you", numberOfLegs: 4)
anim.printProperties()
//打印结果：Is Veg? false. Eats:Can eat you. Number of legs:4
创建子类
class Tiger : Animal{
//Add class specific implementaion
}
var tiger = Tiger(isVeg: false, eats: "Can eat you", numberOfLegs: 4)
tiger.printProperties()
//打印结果：Is Veg? false. Eats:Can eat you. Number of legs:4
需要重写父类中的函数时，需要用override修饰函数名
class Tiger : Animal{
override func printProperties() {
super.printProperties()
print("This is Subclass Tiger")
}
}
var tiger = Tiger(isVeg: false, eats: "Can eat you", numberOfLegs: 4)
tiger.printProperties()
//打印结果：
//Is Veg? false. Eats:Can eat you. Number of legs:4
//This is Subclass Tiger
下面例子是在子类中添加新属性
class Tiger : Animal{
var color : String
override func printProperties() {
//调用父类这个方法，会多打印一个结果，所以在重写父类方法时，也可以不加这个
// super.printProperties()
print("This is tiger Is Veg \(isVeg). Eats:\(eats). Number of legs:\(numberOfLegs).color \(color)")
}
init(isVeg: Bool, eats: String, numberOfLegs: Int,color:String) {
self.color = color
//如果想要在子类中引用父类的属性或函数，使用super.调用
super.init(isVeg: isVeg, eats: eats, numberOfLegs: numberOfLegs)
}
}
var tiger = Tiger(isVeg: false, eats: "Can eat you", numberOfLegs: 4,color: "yellow")
tiger.printProperties()
//打印结果：This is tiger Is Veg false. Eats:Can eat you. Number of legs:4.color yellow
类与结构体的另一个区别就是：类是引用类型的，结构体是值类型
var tiger = Tiger(isVeg: false, eats: "Can eat you", numberOfLegs: 4, color: "White")
tiger.printProperties()
//打印结果：This is tiger Is Veg false. Eats:Can eat you. Number of legs:4.color White
/ar tiger1 = tiger
tiger1.color = "Yellow"
tiger1.printProperties()//打印结果：This is tiger Is Veg false. Eats:Can eat you. Number of legs:4.color Yellow
tiger.printProperties()//打印结果：This is tiger Is Veg false. Eats:Can eat you. Number of legs:4.color Yellow
tiger.eats = "they can eat everything"
tiger1.printProperties()
tiger.printProperties()
//打印结果：This is tiger Is Veg false. Eats:they can eat everything. Number of legs:4.color Yellow
//打印结果：This is tiger Is Veg false. Eats:they can eat everything. Number of legs:4.color Yellow
4.便利初始化：设置属性值的初始值
class A {
var eyes: Int
var legs: Int
init(eyes: Int, legs: Int) {
self.eyes = eyes
self.legs = legs
}
convenience init() {
self.init(eyes: 2, legs: 4)
}
}
var a = A()
print(a.eyes) //prints 2
print(a.legs) //prints 4
便利初始化，只有当类中已经声明了init()时，才可以定义
标签：tiger,color,eats,eat,学习,var,legs,Swift,Class 来源： https://www.cnblogs.com/PotatoToEgg/p/14950456.html
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