如何在Swift中使对象可选

Question

当价值为零时我的应用程序崩溃我怎么能避免这种情况并让蛋糕[“赞”]可选？

我的代码

var likes = [[String:Any]]()

init(cake: [String: Any]){
    self.likes = (cake["likes"] as! [String:Any])["data"] as! [[String:Any]]

}

Answer 1

cake["likes"] 是可选的。标准方法是使用可选绑定。

var likes = [[String:Any]]()

init(cake: [String: Any]) {
    if let likes = cake["likes"] as? [String:Any],
       let data = likes["data"] as? [[String:Any]] {
           self.likes = data
    }
}

Answer 2

试试这样： -

toString()

Answer 3

您也可以使用Guard

 var likes : [[String:Any]]?

    init(cake: [String: Any]?){
        guard let cakeV = cake,let likes = (cakeV["likes"] as? [String:Any]) ,let data = likes ["data"] as?  [[String:Any]] else {
           // IT is nil
            return
        }
        likes = data

}