swift 属性(存储属性、计算属性、懒加载属性、类型属性)

struct Teacher {
    var name = ""
    var age = 0
}

let teacher = Teacher()

//因为 teacher 被声明成了常量，即使name是一个变量属性，也无法修改
teacher.name = "good teacher"   //报错

class Student: NSObject {
    var name = ""
    var age = 0
}

let stu = Student()
stu.name = "good student"

class Student: NSObject {
  lazy var name = ""
  var age = 0
}  

let student = Student()
print(student.name)

class Student: NSObject {
    var firstName = ""
    var lastName = ""
    //定义计算属性
    var fullName:String {
        //定义计算属性的getter方法，该方法的返回值由firstName、lastName两个存储属性决定
        get{
            return firstName + lastName
        }
        //定义计算属性的setter方法(默认名称 newValue)
        set{
            self.firstName = newValue.components(separatedBy: " ")[0]
            self.lastName = newValue.components(separatedBy: " ")[1]
        }
    }
}

let student = Student()
student.fullName = "xiao ming"
print(student.firstName)    //xiao
print(student.lastName)    //ming

class Student: NSObject {
    var firstName = ""
    var lastName = ""
    var fullName:String {
        get{
            return firstName + lastName
        }
    }
}
let student = Student()
student.firstName = "xiao"
student.lastName = "ming"
print(student.fullName)    //xiaoming

class Student: NSObject {
   
    var name:String = "" {
        willSet(newName){
            print("新值是：\(newName)")
        }
        didSet{
            print("旧值是：\(oldValue)")
        }
    }
}
let student = Student()
student.name = "小白"
print("---")
student.name = "小黑"

/*
新值是：小白
旧值是：
---
新值是：小黑
旧值是：小白
*/

class Student: NSObject {
    static var studentNum:Int  = 100
}

print(Student.studentNum)    //100