ios - Swift 中根据 whereKey 解析查询更新或追加

Question

所以我想检查 Parse 中的一个类并检查以下内容:

var query = PFQuery(className:"Score")
query.whereKey("playerName", equalTo:"Bob")
query.whereKey("opponent", equalTo:"Jim")
query.findObjectsInBackgroundWithBlock {
  (objects, error) -> Void in

if error == nil {
if let objects = objects as? [PFObject] {
  for object in objects {
    // if there is a match, update the record
      object["wins"] = 5
  }
} //else if there is no match on the whereKey, append the record to "Score" class.
} else {
// Log details of the failure
println("Error: \(error!) \(error!.userInfo!)")
  }
}

有一个基本功能的小示例代码。如果找到匹配项，我想更新，但如果不存在，则插入它。我正在尝试这样的事情:

query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in

         if error == nil {
              if let objects = objects as? [PFObject] {
                     if objects == [] {
                        //println(objects)
                        }
                     for object in objects {

它没有找到对象，但我不知道如何检测它。必须有一个简单的方法来做到这一点，有人知道吗？

谢谢!

Answer 1

如果将功能分解为逻辑单元，则可以直接实现您正在做的事情。认识到每个程序都是异步运行的，为每个程序提供一个看起来像(也许完全一样)解析 SDK block 的完成 block ...

在您的情况下，您想要找到一个对象，如果它不存在则创建它，并以任何一种方式更新和保存它。我会做类似下面的事情。 (请注意，我写得并不快，并且在这里学到的知识仅足以理解更大的想法):

// record that player named playerName won against opponent named opponent
func playerBeatOpponent(playerName: String, opponent: String, completion: (success: Bool, error: NSError?) -> Void) {
    self.findOrCreateScore(playerName, opponent: opponent, completion: { (scoreObject: PFObject?, error: NSError?) -> Void in
        if let scoreObject = scoreObject {
            let wins = scoreObject["wins"] as! Int
            scoreObject["wins"] = wins + 1
            scoreObject.saveInBackgroundWithBlock(completion)
        }
    })
}

// answer a Score object recording a win between playerName and opponent
// find and return it if it exists, or create it if it doesn't exist
func findOrCreateScore(playerName: String, opponent: String, completion: (scoreObject: PFObject?, error: NSError?) -> Void) {
    self.findScore(playerName, opponent: opponent, completion: { (scoreObject: PFObject?, error: NSError?) -> Void in
        if scoreObject == nil {
            self.createScore(playerName, opponent: opponent, completion: completion)
        } else {
            completion(scoreObject: scoreObject, error: nil)
        }
    })
}

// find a score matching the criteria given
func findScore(playerName: String, opponent: String, completion: (scoreObject: PFObject?, error: NSError?) -> Void) {
    var query = PFQuery(className:"Score")
    query.whereKey("playerName", equalTo:playerName)
    query.whereKey("opponent", equalTo:opponent)
    query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]?, error: NSError?) -> Void in
        if error == nil {
            if let object: AnyObject = objects?[0] {
                completion(scoreObject:object as? PFObject, error: nil)
            } else {
                completion(scoreObject:nil, error: nil)
            }
        } else {
            completion(scoreObject:nil, error: error)
        }
    }
}


// create a new score object with the given params
func createScore(playerName: String, opponent: String, completion: (scoreObject: PFObject?, error: NSError?) -> Void) {
    var scoreObject = PFObject(className:"Score")
    scoreObject["playerName"] = playerName
    scoreObject["oponent"] = opponent
    scoreObject["wins"] = 1
    scoreObject.saveInBackgroundWithBlock { (success: Bool, error: NSError?) -> Void in
        if (success) {
            completion(scoreObject: scoreObject, error: nil)
        } else {
            completion(scoreObject: nil, error: error)
        }
    }
}