Swift 5.X——switch

1.示例1 

import UIKit

var a:Int = 10
switch a {
    case 10:
        print("情况1")//情况1
    case 20:
        print("情况2")
    default:
        print("默认情况")
}

switch a {
    case 10:
        print("情况1")//情况1
    fallthrough//fallthrough会导致不断和后面的case匹配，直到遇到default
    case 20:
        print("情况2")//情况2
    default:
        print("默认情况")
}

2.示例2

import UIKit

var a:String = "a"
switch a {
    case "a","b","c"://abc匹配成功一个即可
        print("情况1")//情况1
    case "d","e":
        print("情况2")
    default:
        print("默认情况")
}

3.示例3

import UIKit

var a:Int = 3
switch a {
    case 1..<5://1,2,3,4匹配成功一个即可
        print("情况1")//情况1
    case 5..<10://5,6,7,8,9匹配成功一个即可
        print("情况2")
    default:
        print("默认情况")
}

4.示例4

import UIKit

var a = (10,20)
switch a {
    case let(name1,name2)://name1对应10，name2对应20
        print("情况1")//情况1
        print("name:\(name1)")//name:10
        print("name:\(name2)")//name:20
    case var(10,name2):
        print("情况2")
    default:
        print("默认情况")
}

5.示例5

import UIKit

var a = (10,20)
switch a {
    case let(name1,name2) where name1>name2://name1对应10，name2对应20，不满足name>name2
        print("情况1")//情况1
    case var(10,name2):
        print("情况2")
    default:
        print("默认情况")
}