刷新Swift 4中的用户默认值

var myVariable = 10
let myConstant = "Hello"

var myOptional: Int? = nil
myOptional = myOptional ?? 0

func getDefault() -> Int {
    return 0
}

var myValue = getDefault()

var myClosure: () -> Int = {
    return 0
}

var myValue = myClosure()