类

import UIKit
class Student {
    var name : String?
    var age : Int = 0
    
    var chineseScore : Double = 0
    var mathScore : Double = 0
    
    //计算属性 ： 通过别的方式计算到结果的属性，称之为计算属性
    var averageScore: Double {
        return (chineseScore + mathScore) * 0.5
    }
    
    //类属性：是和整个类相关的属性，而且是通过类名进行访问
    static var courseCount : Int = 0
    
}

var stu = Student()
//给对象的属性赋值
stu.name = "mark"
stu.age = 18
stu.mathScore = 44.0
stu.chineseScore = 89.00

//给类属性赋值
Student.courseCount = 2

if let name = stu.name {
    print(name)
}
stu.averageScore