import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        //demo44444(name: "老王", age: 10)
        
        demo4(num: "9")
        demo5()
    }

    func demo()  {
        let  name: String? = "老王"
        //  ？?  如果有数值使用默认数值 如果没有值  使用 ？？ 后面的   +  为拼接字符串
        print((name  ?? "")+"你好")
        
         //??优先级低
        print(name  ?? "" + "你好")
    }
    
    
    func demo2()  {
        let  name: String? = "老王"
        //  ？?  如果有数值使用默认数值 如果没有值  使用 ？？ 后面的   +  为拼接字符串
        print((name  ?? "")+"你好")
        
        //??优先级低
        print(name  ?? "" + "你好")
    }
    // 判断非空值
    
    func demo44444(name:String? , age:Int?)  {
       
//        let oName: String? = "老王"
//        let oAge: Int? = 10
        
        
        if let name = name ,
           let  age = age   {
             print(name+String(age))
        }
        
        print("----------")
        
        guard let name = name
            ,   let age = age else {
            print("姓名 或者年龄 为  nil")
            return;
            
        }
        print(name+String(age))  
    }
    // 同一条件满足用，隔开
    
    func demo4(num : String)  {
        switch num {
        case "10" ,"9":
            print("优秀")
        default:
             print("一般")
        }
    }
    
    func demo5()  {
       // [0,5)
        for i in 0..<5 {
            print(i)
        }
        
        print("------")
     
        // [0,5]
        for i in 0...5 {
            print(i)
        }
         print("------")
        for i in 1..<5.revesed {
            print(i)
        }
    }
    
}