objective-c - 如果错误 == nil swift 解析

Question

如果出现问题，我正在尝试检查何时将对象保存到我的解析服务。但我有两个选择，我有三个选择，但我不知道有什么区别。我有这三个选项(if error == nil，或 if object != nil，或 if error == nil and object != nil)。我应该使用哪一个。谢谢

选项#1

let user = PFUser.current()!
user.saveInBackground (block: { (success:Bool, error:Error?) -> Void in
    if error == nil{
    }
)}

选项#2

let user = PFUser.current()!
user.saveInBackground (block: { (success:Bool, error:Error?) -> Void in
    if object != nil{
    }
)}

选项#3

let user = PFUser.current()!
user.saveInBackground (block: { (success:Bool, error:Error?) -> Void in
    if error == nil && object != nil{
    }
)}

Answer 1

我建议并鼓励你使用 guard 语句，它是为这种情况而设计的。

    //Always safely unwrap optional value:
    if let user = PFUser.current(){

    user.saveInBackground (block: { (success:Bool, error:Error?) -> Void in

        guard success, error == nil else {
        //handle error somehow...(print or whatever...)
        return
         }
       //Continue here as everything is fine...

    )}
}