北京的雾霾为什么没了 wumai( 四 )


return a > b
}
var hahArray = array.sorted(by: daoxu)
print(hahArray)
//用闭包表达式进行改写
var cityArray = array.sorted { (a, b) -> Bool in
return a>b
}
print(cityArray)
//输出["D", "C", "B", "A"]
//这就是闭包写法
//参数和“返回类型”可自动推断,单表达式可以忽略“return”关键词
var cityArray2 = array.sorted { (a, b) in
a>b
}
print(cityArray2)
//使用快捷参数,前缀$,从0开始递增
var cityArray3 = array.sorted{
$0 > $1
}
print("\(cityArray3)")
/*
输出
["D", "C", "B", "A"]
*/
*/
enum Weather {
case sunny
case cloudy
case rainy
case snow
case froggy
}
print(Weather.sunny)
var todayWeather = Weather.sunny
switch todayWeather {
case .cloudy:
print("今天天气多云")
case .sunny:
print("今天天气晴朗")
case .rainy:
print("今天天气下雨")
default:
break
}
//输出今天天气晴朗
enum tianqi {
case qing(Int,Int,String)
case mai(String,Int)
}
//附上附加值:加上元组字面量
let shanghaiTianQi = tianqi.qing(30, 50, "湛蓝")
let shanghaiwumai = tianqi.mai("PM2.5", 100)
switch shanghaiwumai {
case .qing(let ziwai,let liangshai,let dec):
print("紫外指数:",ziwai,"晾晒:",liangshai,"天颜色:",dec)
case .mai(let leibie,let index):
print("类别:",leibie,"指数",index)
}
switch shanghaiTianQi {
case .qing(let ziwai,let liangshai,let dec):
print("紫外指数:",ziwai,"晾晒:",liangshai,"天颜色:",dec)
case .mai(let leibie,let index):
print("类别:",leibie,"指数",index)
}
/*输出
类别: PM2.5 指数 100
紫外指数: 30 晾晒: 50 天颜色: 湛蓝
*/


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