Getter在Swift 3中的setter

I'm using this variable

我正在使用这个变量

public var tick: Int64 {
    get {
        return UserDefaults.standard.object(forKey: TICK) as? Int64 ?? 0
    }
    set(v) {
        let cur = UserDefaults.standard.object(forKey: TICK) as? Int64 ?? 0 + v
        UserDefaults.standard.set(cur, forKey: TICK)
    }
}
public va