Question

如果出现问题，我试图检查何时将对象保存到我的解析服务中。但我有两个选择，我有三个选择，我不知道其中的区别。我有这三个选项（如果error == nil，或者如果object！= nil，或者如果error == nil and object！= nil）。我应该使用哪一个。感谢

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

最好使用不同的处理程序来获得成功和失败：

func saveInBackground(success: () -> Void, failure: (Error?) -> Void) {
    /* do whatever you need */
    if saved {
        success()
    } else {
        failure(saveError)
    }
}

saveInBackground(success: {
    /* saving was succeed */
}, failure: { (error) in
    /* saving was failed */
})

Answer 2

保存操作成功时不应该出现错误，一般来说，这取决于您实施的后续步骤。没有一种方法是无效的，我仍然建议您在检查错误之前检查'happy value'，object，success dtc ...

Answer 3

我建议并鼓励你使用保护声明，这是针对这种情况所做的。

    //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...

    )}
}

if error == nil parse swift

3 个答案: