Question

在我的应用程序中，我有一个本地SQLite数据库并使用解析服务器（Back4App.com）。这两者的原因是允许用户设备之间的同步，如果用户删除并稍后重新安装应用程序，则可以下载数据。

我正在使用解析签名功能。登录后，我检查本地数据库是否有数据，如果没有，我去Parse并从那里下载然后将数据插入本地数据库。

奇怪的是事件的顺序并没有像我期望的那样发生，这就是我的问题所在。

SigninVC如下：

@IBAction func signinButton(sender: UIButton) {

    activityIndicator.startAnimating()

    // hides keyboard
    self.view.endEditing(true)


    // if username or password is empty
    if usernameTextField.text!.isEmpty || passwordTextField.text!.isEmpty {


        SCLAlertView().showError("Opps".localized, subTitle: "missingDetail1".localized)

    }

    // login functions
    PFUser.logInWithUsername(inBackground: self.usernameTextField.text!, password: self.passwordTextField.text!) {
        (user: PFUser?, error: Error?) -> Void in
        if let error = error {
            if let errorString = (error as NSError).userInfo["error"] as? String {
                self.activityIndicator.stopAnimating()
                NSLog(errorString);
                SCLAlertView().showError("Error".localized, subTitle: "loginError".localized)
            }
        } else {

            self.userDefault.set(PFUser.current()!.username, forKey: "username")
            self.userDefault.synchronize()
            self.activityIndicator.stopAnimating()
            self.signInCompleted ()
        }


        self.rlDatabase.checkForEmtpySpeciesDetail ()

        let datbaseCheckResult = self.userDefault.bool (forKey: "databaseEmpty")

        if datbaseCheckResult == true {

            print("No data in RLDatabase, now checking if Parse has Data")

            print("1 Calling downloadFromParse function")


            self.downloadFromParse { [weak self] in

                print("6 Calling insertParseToSQLite function")

                self?.rlDatabase.insertParseToSQLite()
            }


        } else {

//                print("Database Not empty, no update needed")

        }

    }
}

func downloadFromParse (_ completion: ()->()) {

    print("2 Starting downloadFromParse function")

    userDefault.bool (forKey: "parseHasData")

    var userCommonNameArray = parseArrayModel.userCommonNameArray
    var userCommonNameESArray = parseArrayModel.userCommonNameESArray
    var userCommonNameFRArray = parseArrayModel.userCommonNameFRArray
    var userCommonNameDEArray = parseArrayModel.userCommonNameDEArray
    var speciesNameArray = parseArrayModel.speciesNameArray
    var userNotesArray = parseArrayModel.userNotesArray


    let downloadQuery = PFQuery(className:"ReefLifeApps")
    downloadQuery.whereKey("username", equalTo: PFUser.current()!.username!)

    downloadQuery.findObjectsInBackground {(downloadedData, error) -> Void in
        if error == nil {

            print("3 begining downloadQuery")

            for downloadData in downloadedData! {

                userCommonNameArray.append(downloadData.object(forKey: "userCommonName") as! String)
                userCommonNameESArray.append(downloadData.object(forKey: "userCommonNameES") as! String)
                userCommonNameFRArray.append(downloadData.object(forKey: "userCommonNameFR") as! String)
                userCommonNameDEArray.append(downloadData.object(forKey: "userCommonNameDE") as! String)
                speciesNameArray.append(downloadData.object(forKey: "speciesName") as! String)
                userNotesArray.append(downloadData.object(forKey: "userNotes") as! String)

                print (speciesNameArray)

                print("4 finished downloadQuery")

            }

        } else {

            self.userDefault.set(false, forKey: "parseHasData")

//                print("No username registered in parse")

        }
    }

    if speciesNameArray.isEmpty == true {
        self.userDefault.set(false, forKey: "parseHasData")
    } else {
        self.userDefault.set(true, forKey: "parseHasData")
    }
    completion()

    print("5 finished downloadFromParse function")

}

RLDatabase.swift具有SQLite插入

func insertParseToSQLite () {

    print("7 begining insertParseToSQLite function")

    let parseCheckResult = self.userDefault.bool (forKey: "parseHasData")

    if parseCheckResult == true {

        let userCommonNameArray = parseArrayModel.userCommonNameArray
        let userCommonNameESArray = parseArrayModel.userCommonNameESArray
        let userCommonNameFRArray = parseArrayModel.userCommonNameFRArray
        let userCommonNameDEArray = parseArrayModel.userCommonNameDEArray
        let speciesNameArray = parseArrayModel.speciesNameArray
        let userNotesArray = parseArrayModel.userNotesArray


            var statement: OpaquePointer? = nil

            let update = String(format:"UPDATE RL_Species SET user_common_name = '\(userCommonNameArray)', user_common_name_fr = '\(userCommonNameFRArray)', user_common_name_es = '\(userCommonNameESArray)', user_common_name_de = '\(userCommonNameDEArray)', user_notes = '\(userNotesArray)' WHERE RL_Species.specie = '\(speciesNameArray)';")

        print("8 starting SQLite3 insert")

            if sqlite3_prepare_v2(database, update, -1, &statement, nil) == SQLITE_OK {

                if sqlite3_step(statement) == SQLITE_DONE {
//                        print("Successfully updated database with Parse data.")
                } else {
//                        print("Could NOT Update database with Parse data.")
                }

            } else {

                // forces SQLite to send error messagesddd
                let errorMessage = String.init(validatingUTF8: sqlite3_errmsg(database))!
                print("update failed! \(errorMessage)")
        }

            sqlite3_finalize(statement)

    } else {

    }

    print("9 finishing insertParseToSQLite function")

}

ParseArrayModel.swift

struct ParseArrayModel
{
    var userCommonNameArray = [String]()
    var userCommonNameESArray = [String]()
    var userCommonNameFRArray = [String]()
    var userCommonNameDEArray = [String]()
    var speciesNameArray = [String]()
    var userNotesArray = [String]()

}

如您所见，第一个调用是从Parse下载，然后调用insert函数。然而，正在发生的事情是它发送到downloadFromParse，但是在

之后

downloadQuery.findObjectsInBackground {(downloadedData, error) -> Void in

它跳过函数的其余部分，然后转到insertToSQLite函数，因为数组中没有数据，所以没有插入任何内容。然后它返回到DownloadFromParse，然后抓取数据。所以，最后，所有数据都在那里，但是在错误的事件序列中。

完全难倒。非常感谢任何帮助。

编辑：添加//打印行以在更新后显示订单。

以下是控制台显示的内容：

No data in RLDatabase, now checking if Parse has Data
1 Calling downloadFromParse function
2 Starting downloadFromParse function
6 Calling insertParseToSQLite function
7 begining insertParseToSQLite function
9 finishing insertParseToSQLite function
5 finished downloadFromParse function
3 begining downloadQuery
["Acanthaster planci"]
4 finished downloadQuery

Answer 1

这是因为您在后台下载异步，因此您的代码将在该过程正在进行时继续执行。您需要创建一个回调以告知下载完成后，然后您可以调用下一个函数。

func downloadFromParse (_ completion: ()->()) {

userDefault.bool (forKey: "parseHasData")

var userCommonNameArray = parseArrayModel.userCommonNameArray
var userCommonNameESArray = parseArrayModel.userCommonNameESArray
var userCommonNameFRArray = parseArrayModel.userCommonNameFRArray
var userCommonNameDEArray = parseArrayModel.userCommonNameDEArray
var speciesNameArray = parseArrayModel.speciesNameArray
var userNotesArray = parseArrayModel.userNotesArray


let downloadQuery = PFQuery(className:"ReefLifeApps")
downloadQuery.whereKey("username", equalTo: PFUser.current()!.username!)

downloadQuery.findObjectsInBackground {(downloadedData, error) -> Void in
    if error == nil {

        for downloadData in downloadedData! {

            userCommonNameArray.append(downloadData.object(forKey: "userCommonName") as! String)
            userCommonNameESArray.append(downloadData.object(forKey: "userCommonNameES") as! String)
            userCommonNameFRArray.append(downloadData.object(forKey: "userCommonNameFR") as! String)
            userCommonNameDEArray.append(downloadData.object(forKey: "userCommonNameDE") as! String)
            speciesNameArray.append(downloadData.object(forKey: "speciesName") as! String)
            userNotesArray.append(downloadData.object(forKey: "userNotes") as! String)

            print (speciesNameArray)


        }

    } else {

        self.userDefault.set(false, forKey: "parseHasData")

        print("No username registered in parse")

    }
}

if speciesNameArray.isEmpty == true {
    self.userDefault.set(false, forKey: "parseHasData")
} else {
    self.userDefault.set(true, forKey: "parseHasData")
}
 completion()
}

然后你可以这样做：

 downloadFromParse { [weak self] in
     // call next function knowing the parse download is complete.
 }

Answer 2

我发布的结果是为了帮助那些想要将数据从解析服务器传输到本地数据库的人，在我的例子中是SQLite。

我没有尝试在调用insertToSQLite func之前完成下载，而只需要在查询调用中添加insertToSQLite func。

还有一些其他程序员错误。以下是测试后的结果：

var userCommonNameArray = String()
var userCommonNameESArray = String()
var userCommonNameFRArray = String()
var userCommonNameDEArray = String()
var speciesNameArray = String()
var userNotesArray = String()
var speciesIDArray = Int()

func txFromParseToSQLite () {

    let downloadQuery = PFQuery(className:"ReefLifeApps")

    downloadQuery.whereKey("username", equalTo: PFUser.current()!.username!)

    downloadQuery.findObjectsInBackground {(downloadedData, error) -> Void in
        if error == nil {

            if (downloadedData?.count == 0) {

                print("DownloadData.count == 0")

                return

            } else {

                if let downloadedData = downloadedData {
                    for downloadData in downloadedData {

                        self.userCommonNameArray = downloadData["userCommonName"] as! String
                        self.userCommonNameFRArray = downloadData["userCommonNameFR"] as! String
                        self.userCommonNameESArray = downloadData["userCommonNameES"] as! String
                        self.userCommonNameDEArray = downloadData["userCommonNameDE"] as! String
                        self.userNotesArray = downloadData["userNotes"] as! String
                        self.speciesNameArray = downloadData["speciesName"] as! String
                        self.speciesIDArray = downloadData["speciesID"] as! Int

                        print (downloadData)

                        self.insertParseToSQLite ()
                    }
                }
            }
        }
    }
}

func insertParseToSQLite () {

        var statement: OpaquePointer? = nil

        let update = String(format:"UPDATE RL_User SET user_common_name = '\(userCommonNameArray)', user_common_name_fr = '\(userCommonNameFRArray)', user_common_name_es = '\(userCommonNameESArray)', user_common_name_de = '\(userCommonNameDEArray)', user_notes = '\(userNotesArray)', speciesName = '\(speciesNameArray)' WHERE id = \(speciesIDArray);")

        if sqlite3_prepare_v2(databaseUser, update, -1, &statement, nil) == SQLITE_OK {

            if sqlite3_step(statement) == SQLITE_DONE {
            } else {
            }

        } else {
            let errorMessage = String.init(validatingUTF8: sqlite3_errmsg(databaseUser))!
            print("update failed! \(errorMessage)")
        }
    sqlite3_finalize(statement)
}

从解析服务器到本地sqlite（Swift 3）

2 个答案: