where判断

let point = (3,3)
switch point {
case let (x,y) where x == y
    print("xxxxx")
default:
    print("yyyyy")
}

let age = 123
if case 10...19 = age where age >= 10 {
print("acv")
}

if case xxx = age是把age判断一下在不在case里

where就是继续限定条件在一个bool的范围内