关于Swift if for while case

        let value = 20
        
        if (value > 20)
        {
            print("大于20")
        }
        else if (value < 20)
        {
            print("小于20")
        }
        else
        {
            print("等于20")
        }
        
        let switchCondition:String = "jzh"
        switch switchCondition
        {
        case "jzh":
            print("ok jzh");
            fallthrough
        case "jiang":
            print("ok jiang");
            fallthrough
        default:
            print("ok idodo")
            
        }
        
        let price = 100
        
        switch price
        {
        case 0:
            print("免费")
        case 10..<50:
            print("超低价")
        case 50..<100:
            print("低价")
        case 100...500:
            print("价格适中")
        case 501...999_999_999:
            print("贵")
        default:
            print("非常贵")
        }
        
        for index in 1...5
        {
            print("\(index)")
        }
        
        let names = ["a", "b", "c", "d"]
        for name in names
        {
            print("Hello, \(name)!")
        }
        
        var index = 10
        
        while index < 20
        {
            print( "index 的值为 \(index)")
            index = index + 1
        }