我将简要解释一下情况。 我正在构建一个测验应用程序，我希望它主要使用互联网，但也可以在用户断开连接时工作一段时间。我使用的旧代码仅使用同步查询，它花费的时间比我预期的要多。所以我决定重新制定它。 我预测的情况如下：
当我的用户选择主题时，应用会同步为每个子主题提出1个问题，以便为我做好准备用户点击并加快速度。
在得到第一个问题之后，应用程序将为每个子主题 异步获得另外4个（或需要多少才能完成5个），当用户被占用时回答提交给他的第一个问题。
最后，应用程序会将对象保存在本地数据存储区中，这样用户可以在未连接时为每个子主题回答5个问题。
这是我的代码：
func getQuestionsRemotelyandSave (subsubject:String?, subject:String?, arrayOfSubsubjects:[String]?) {
self.getFromUserDefaults()
if Reachability.isConnectedToNetwork() == true {
if self.needsToGetQuestions == true {
let user = PFUser.currentUser()
var query = PFQuery(className: "Questions")
query.whereKey("answeredBy", equalTo: user)
query.whereKey("grade", equalTo: user["grade"])
if subsubject != nil && subject == nil {
query.whereKey("subsubject", equalTo: subsubject)
query.limit = 2
let array = query.findObjects()
for item in array {
let object = item as PFObject
var QuestionToPin = PFObject(className: "Questions")
QuestionToPin["Question"] = object["Question"] as String
QuestionToPin["rightAnswer"] = object ["rightAnswer"] as String
QuestionToPin["wrongAnswer1"] = object ["wrongAnswer1"] as String
QuestionToPin["wrongAnswer2"] = object ["wrongAnswer2"] as String
QuestionToPin["wrongAnswer3"] = object ["wrongAnswer3"] as String
QuestionToPin["grade"] = object["grade"] as String
QuestionToPin["subject"] = object ["subject"] as String
QuestionToPin["subsubject"] = object ["subsubject"] as String
QuestionToPin["feedback"] = object ["feedback"] as? String
QuestionToPin["shortFeedback1"] = object ["shortFeedback1"] as? String
QuestionToPin["shortFeedback2"] = object ["shortFeedback2"] as? String
QuestionToPin["shortFeedback3"] = object ["shortFeedback3"] as? String
QuestionToPin.pin()
}
query.limit = 3
query.findObjectsInBackgroundWithBlock({ (objects:[AnyObject]!, error:NSError!) -> Void in
if error == nil {
let questions = objects as [PFObject]
var QuestionsToPin = [PFObject]()
for object in questions {
var QuestionToPin = PFObject(className: "Questions")
QuestionToPin["Question"] = object["Question"] as String
QuestionToPin["rightAnswer"] = object ["rightAnswer"] as String
QuestionToPin["wrongAnswer1"] = object ["wrongAnswer1"] as String
QuestionToPin["wrongAnswer2"] = object ["wrongAnswer2"] as String
QuestionToPin["wrongAnswer3"] = object ["wrongAnswer3"] as String
QuestionToPin["grade"] = object["grade"] as String
QuestionToPin["subject"] = object ["subject"] as String
QuestionToPin["subsubject"] = object ["subsubject"] as String
QuestionToPin["feedback"] = object ["feedback"] as? String
QuestionToPin["shortFeedback1"] = object ["shortFeedback1"] as? String
QuestionToPin["shortFeedback2"] = object ["shortFeedback2"] as? String
QuestionToPin["shortFeedback3"] = object ["shortFeedback3"] as? String
QuestionToPin.pinInBackground()
}
}
})
}
if subsubject == nil && subject != nil {
var firstTime = true
var semaphore = dispatch_semaphore_create(0)
query.limit = 1
for item in arrayOfSubsubjects! {
if item != "Todas as matérias" {
var query3 = PFQuery(className: "Questions")
query3.fromLocalDatastore()
query3.whereKey("subsubject", equalTo: item)
let count = query3.countObjects()
if count == 0 {
query.whereKey("subsubject", equalTo: item)
let array:NSArray = query.findObjects()
for item in array {
let object = item as PFObject
var QuestionToPin = PFObject(className: "Questions")
QuestionToPin["Question"] = object["Question"] as String
QuestionToPin["rightAnswer"] = object ["rightAnswer"] as String
QuestionToPin["wrongAnswer1"] = object ["wrongAnswer1"] as String
QuestionToPin["wrongAnswer2"] = object ["wrongAnswer2"] as String
QuestionToPin["wrongAnswer3"] = object ["wrongAnswer3"] as String
QuestionToPin["grade"] = object["grade"] as String
QuestionToPin["subject"] = object ["subject"] as String
QuestionToPin["subsubject"] = object ["subsubject"] as String
QuestionToPin["feedback"] = object ["feedback"] as? String
QuestionToPin["shortFeedback1"] = object ["shortFeedback1"] as? String
QuestionToPin["shortFeedback2"] = object ["shortFeedback2"] as? String
QuestionToPin["shortFeedback3"] = object ["shortFeedback3"] as? String
QuestionToPin.pin()
}
}
if count > 0 {
var limit = 5 - count
if limit < 0 {
limit = 0
}
query.limit = limit
if firstTime == false {
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
}
query.findObjectsInBackgroundWithBlock({ (objects:[AnyObject]!, error:NSError?) -> Void in
if error == nil {
let questions = objects as [PFObject]
for object in questions {
var QuestionToPin = PFObject(className: "Questions")
QuestionToPin["Question"] = object["Question"] as String
QuestionToPin["rightAnswer"] = object ["rightAnswer"] as String
QuestionToPin["wrongAnswer1"] = object ["wrongAnswer1"] as String
QuestionToPin["wrongAnswer2"] = object ["wrongAnswer2"] as String
QuestionToPin["wrongAnswer3"] = object ["wrongAnswer3"] as String
QuestionToPin["grade"] = object["grade"] as String
QuestionToPin["subject"] = object ["subject"] as String
QuestionToPin["subsubject"] = object ["subsubject"] as String
QuestionToPin["feedback"] = object ["feedback"] as? String
QuestionToPin["shortFeedback1"] = object ["shortFeedback1"] as? String
QuestionToPin["shortFeedback2"] = object ["shortFeedback2"] as? String
QuestionToPin["shortFeedback3"] = object ["shortFeedback3"] as? String
QuestionToPin.pinInBackground()
}
dispatch_semaphore_signal(semaphore)
firstTime = false
}
})
}
}
}
}
}
}
}
我面临的问题是我无法从Parse请求多个异步函数。我想的可能是等待异步函数在另一个函数启动之前完成，但我希望它能在没有用户等待的情况下发生。有办法吗？
谢谢。