Swift：按顺序多个异步请求。如何等待上一个请求完成？
作为我应用程序中身份验证过程的一部分，用户可以使用他们的Facebook帐户登录-我正在使用Facebook iOS SDK来处理此过程。身份验证完成后，我向Facebook graph api发出请求，以获取用户配置文件数据（这是第一个异步请求）。第二个异步请求也是向Facebook graph api请求安装了应用程序的用户好友列表 此函数中的最后一个和第三个请求向我开发的API发出异步POST请求，该API用于发布从Facebook收集的所有数据。最后，完成此操作后，允许用户进入应用程序。然而事实并非如此，Facebook的请求似乎没有在向API发送POST请求之前完成，因此它推送了空白数据。我不介意前两个Facebook请求的完成顺序，但是我需要在允许用户进入应用程序之前将数据成功发布到API。我尝试过使用信号量和调度组，但是当查看控制台时，事情并没有以正确的顺序运行，我可以从API数据库中看到正在插入空值 身份验证控制器Swift：按顺序多个异步请求。如何等待上一个请求完成？,swift,api,http,facebook-graph-api,asynchronous,Swift,Api,Http,Facebook Graph Api,Asynchronous,作为我应用程序中身份验证过程的一部分，用户可以使用他们的Facebook帐户登录-我正在使用Facebook iOS SDK来处理此过程。身份验证完成后，我向Facebook graph api发出请求，以获取用户配置文件数据（这是第一个异步请求）。第二个异步请求也是向Facebook graph api请求安装了应用程序的用户好友列表 此函数中的最后一个和第三个请求向我开发的API发出异步POST请求，该API用于发布从Facebook收集的所有数据。最后，完成此操作后，允许用户进入应用程序。
// Successful login, fetch faceook profile
let group = DispatchGroup()
group.enter()
// Redirect to tab bar controller should not happen until fetchProfile() has finished
// Redirect should not happen if fetchProfile() errors
self.fetchProfile()
group.leave()
// Redirect to tab bar controller
let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let tabBarController = storyboard.instantiateViewController(withIdentifier: "tabBarController") as! UITabBarController
self.present(tabBarController, animated: true, completion: nil)
// Facebook Profile Request
func fetchProfile() {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "User")
let user = appDelegate.user
var facebookFriends = [String?]()
do {
let results = try managedContext?.fetch(fetchRequest)
fetchedUser = results![0] as? NSManagedObject
}
catch {
print("Error fetching User entity")
return
}
let group = DispatchGroup()
print("Starting Step 1")
group.enter()
// Facebook Profile
let parameters = ["fields": "id, email, first_name, last_name, picture.width(500).height(500), birthday, gender"]
FBSDKGraphRequest(graphPath: "me", parameters: parameters).start { (connection, result, error) -> Void in
if error != nil {
print(error)
return
}
let result = result as? NSDictionary
if let providerID = result?["id"] as? String {
user.provider_id = providerID
self.fetchedUser!.setValue(providerID, forKey: "provider_id")
}
if let firstName = result?["first_name"] as? String {
user.first_name = firstName
self.fetchedUser!.setValue(firstName, forKey: "first_name")
}
if let lastName = result?["last_name"] as? String {
user.last_name = lastName
self.fetchedUser!.setValue(lastName, forKey: "last_name")
}
if let email = result?["email"] as? String {
user.email = email
self.fetchedUser!.setValue(email, forKey: "email")
}
if let picture = result?["picture"] as? NSDictionary, let data = picture["data"] as? NSDictionary, let url = data["url"] as? String {
user.avatar = url
self.fetchedUser!.setValue(url, forKey: "avatar")
}
if let birthday = result?["birthday"] as? String {
user.birthday = birthday
self.fetchedUser!.setValue(sqlDate, forKey: "birthday")
}
if var gender = result?["gender"] as? String {
user.gender = gender
self.fetchedUser!.setValue(gender, forKey: "gender")
}
group.leave()
print("Step 1 Done")
group.enter()
print("Starting Step 2")
// Facebook Friends Request
FBSDKGraphRequest(graphPath: "me/friends", parameters: ["fields": "id, first_name, last_name, picture"]).start { (connection, result, error) -> Void in
if error != nil {
print(error)
return
}
let result = result as! [String:AnyObject]
for friend in result["data"] as! [[String:AnyObject]] {
let id = friend["id"] as! String
facebookFriends.append(id)
}
group.leave()
print("Step 2 Done")
// User POST Request
var dictionary = self.fetchedUser?.dictionaryWithValues(forKeys: ["provider", "provider_id", "first_name", "last_name", "email", "avatar", "birthday", "gender"])
if facebookFriends.count > 0 {
dictionary?["friends"] = facebookFriends
}
let data = NSMutableDictionary()
data.setValuesForKeys(dictionary!)
//let semaphore = DispatchSemaphore(value: 2)
group.enter()
print("Starting Step 3")
do {
// Here "jsonData" is the dictionary encoded in JSON data
let jsonData = try JSONSerialization.data(withJSONObject: data, options: .prettyPrinted)
// Here "decoded" is of type `Any`, decoded from JSON data
let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
// Final dict
if let dictFromJSON = decoded as? [String:String] {
let endpoint = "http://endpoint.com/user"
let url = URL(string: endpoint)
let session = URLSession.shared
var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.httpBody = try JSONSerialization.data(withJSONObject: dictFromJSON, options: [])
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
session.dataTask(with: request, completionHandler: { (data, response, error) -> Void in
if error != nil {
//semaphore.signal()
group.leave()
print(error)
return
}
do {
// Save response
let json = try(JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [String: AnyObject])
if let userID = json?["user_id"] {
user.user_id = userID as? Int
self.fetchedUser!.setValue(userID, forKey: "user_id")
}
if let friends = json?["friends"] , !(friends is NSNull){
user.friends = friends as? [String]
self.fetchedUser!.setValue(friends, forKey: "friends")
}
group.leave()
//semaphore.signal()
} catch let jsonError {
print(jsonError)
return
}
}).resume()
}
} catch {
print(error.localizedDescription)
}
// Wait to async task to finish before moving on
//_ = semaphore.wait(timeout: DispatchTime.distantFuture)
print("Step 3 Done")
}
}
}
//Facebook个人资料请求
func fetchProfile（）{
让appDelegate=UIApplication.shared.delegate为！appDelegate
让managedContext=appDelegate.managedObjectContext
let fetchRequest=NSFetchRequest（entityName:“用户”）
让user=appDelegate.user
var facebookFriends=[String？]（）
做{
让结果=尝试managedContext？.fetch（fetchRequest）
fetchedUser=results！[0]作为？NSManagedObject
}
抓住{
打印（“获取用户实体时出错”）
返回
}
let group=DispatchGroup（）
打印（“开始步骤1”）
group.enter（）
//Facebook个人资料
let parameters=[“fields”：“id、电子邮件、名字、姓氏、图片、宽度（500）、高度（500）、生日、性别”]
FBSDKGraphRequest（graphPath:“me”，参数：parameters）。开始{（连接、结果、错误）->Void in
如果错误！=nil{
打印（错误）
返回
}
让结果=结果为？NSDictionary
如果让providerID=result？[“id”]作为字符串{
user.provider\u id=providerID
self.fetchedUser！.setValue（providerID，forKey:“provider\u id”）
}
如果让firstName=result？[“first_name”]作为？字符串{
user.first\u name=firstName
self.fetchedUser！.setValue（firstName，forKey:“first_name”）
}
如果让lastName=result？[“last_name”]作为？字符串{
user.last_name=lastName
self.fetchedUser！.setValue（lastName，forKey:“last_name”）
}
如果让email=result？[“email”]作为？字符串{
user.email=电子邮件
self.fetchedUser！.setValue（电子邮件，forKey:“电子邮件”）
}
如果让picture=result？[“picture”]作为NSDictionary，让data=picture[“data”]作为NSDictionary，让url=data[“url”]作为字符串{
user.avatar=url
self.fetchedUser！.setValue（url，forKey:“化身”）
}
如果让生日=结果？[“生日”]作为？字符串{
user.birth=生日
self.fetchedUser！.setValue（sqlDate，forKey:“生日”）
}
如果变量性别=结果？[“性别”]为？字符串{
user.gender=性别
self.fetchedUser！.setValue（性别，forKey:“性别”）
}
小组请假（）
打印（“步骤1完成”）
group.enter（）
打印（“开始步骤2”）
//Facebook好友请求
FBSDKGraphRequest（graphPath:“我/朋友”，参数：[“字段”：“id，名字，姓氏，图片”]）。开始{（连接，结果，错误）->在
如果错误！=nil{
打印（错误）
返回
}
让result=结果为！[字符串：AnyObject]
对于结果中的好友[“数据”]为！[[String:AnyObject]]{
让id=friend[“id”]作为！字符串
facebookFriends.append（id）
}
小组请假（）
打印（“第2步完成”）
//用户POST请求
var dictionary=self.fetchedUser？.dictionaryWithValue（forKeys:[“提供商”、“提供商id”、“名字”、“姓氏”、“电子邮件”、“化身”、“生日”、“性别”]）
如果facebookFriends.count>0{
字典？[“朋友”]=facebookFriends
}
let data=NSMutableDictionary（）
data.setValuesForKeys（字典！）
//让信号量=分派信号量（值：2）
group.enter（）
打印（“开始步骤3”）
做{
//这里的“jsonData”是用JSON数据编码的字典
让jsonData=try JSONSerialization.data（使用jsonObject:data，选项：。预打印）
//这里的“decoded”是“Any”类型，从JSON数据解码
let decoded=尝试JSONSerialization.jsonObject（使用：jsonData，选项：[]）
//最后的格言
如果让dictFromJSON=解码为？[String:String]{
让端点=”http://endpoint.com/user"
让url=url（字符串：端点）
让session=URLSession.shared
var request=URLRequest（url:url！）
request.httpMethod=“POST”
request.httpBody=try JSONSerialization.data（使用JSONObject:dictFromJSON，选项：[]）
request.addValue（“application/json”，forHTTPHeaderField:“Accept”）
request.addValue（“应用程序/json”，forHTTPHeaderField:“内容类型”）
dataTask（with:request，completionHandler:{（数据，响应，错误）->中的Void
如果错误！=n
// Facebook Profile Request
func fetchProfile() {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "User")
let user = appDelegate.user
var facebookFriends = [String?]()
do {
let results = try managedContext?.fetch(fetchRequest)
fetchedUser = results![0] as? NSManagedObject
}
catch {
print("Error fetching User entity")
return
}
let group = DispatchGroup()
print("Starting Step 1")
group.enter()
// Facebook Profile
let parameters = ["fields": "id, email, first_name, last_name, picture.width(500).height(500), birthday, gender"]
FBSDKGraphRequest(graphPath: "me", parameters: parameters).start { (connection, result, error) -> Void in
if error != nil {
print(error)
return
}
let result = result as? NSDictionary
if let providerID = result?["id"] as? String {
user.provider_id = providerID
self.fetchedUser!.setValue(providerID, forKey: "provider_id")
}
if let firstName = result?["first_name"] as? String {
user.first_name = firstName
self.fetchedUser!.setValue(firstName, forKey: "first_name")
}
if let lastName = result?["last_name"] as? String {
user.last_name = lastName
self.fetchedUser!.setValue(lastName, forKey: "last_name")
}
if let email = result?["email"] as? String {
user.email = email
self.fetchedUser!.setValue(email, forKey: "email")
}
if let picture = result?["picture"] as? NSDictionary, let data = picture["data"] as? NSDictionary, let url = data["url"] as? String {
user.avatar = url
self.fetchedUser!.setValue(url, forKey: "avatar")
}
if let birthday = result?["birthday"] as? String {
user.birthday = birthday
self.fetchedUser!.setValue(sqlDate, forKey: "birthday")
}
if var gender = result?["gender"] as? String {
user.gender = gender
self.fetchedUser!.setValue(gender, forKey: "gender")
}
group.leave()
print("Step 1 Done")
group.enter()
print("Starting Step 2")
// Facebook Friends Request
FBSDKGraphRequest(graphPath: "me/friends", parameters: ["fields": "id, first_name, last_name, picture"]).start { (connection, result, error) -> Void in
if error != nil {
print(error)
return
}
let result = result as! [String:AnyObject]
for friend in result["data"] as! [[String:AnyObject]] {
let id = friend["id"] as! String
facebookFriends.append(id)
}
group.leave()
print("Step 2 Done")
// User POST Request
var dictionary = self.fetchedUser?.dictionaryWithValues(forKeys: ["provider", "provider_id", "first_name", "last_name", "email", "avatar", "birthday", "gender"])
if facebookFriends.count > 0 {
dictionary?["friends"] = facebookFriends
}
let data = NSMutableDictionary()
data.setValuesForKeys(dictionary!)
//let semaphore = DispatchSemaphore(value: 2)
group.enter()
print("Starting Step 3")
do {
// Here "jsonData" is the dictionary encoded in JSON data
let jsonData = try JSONSerialization.data(withJSONObject: data, options: .prettyPrinted)
// Here "decoded" is of type `Any`, decoded from JSON data
let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
// Final dict
if let dictFromJSON = decoded as? [String:String] {
let endpoint = "http://endpoint.com/user"
let url = URL(string: endpoint)
let session = URLSession.shared
var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.httpBody = try JSONSerialization.data(withJSONObject: dictFromJSON, options: [])
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
session.dataTask(with: request, completionHandler: { (data, response, error) -> Void in
if error != nil {
//semaphore.signal()
group.leave()
print(error)
return
}
do {
// Save response
let json = try(JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [String: AnyObject])
if let userID = json?["user_id"] {
user.user_id = userID as? Int
self.fetchedUser!.setValue(userID, forKey: "user_id")
}
if let friends = json?["friends"] , !(friends is NSNull){
user.friends = friends as? [String]
self.fetchedUser!.setValue(friends, forKey: "friends")
}
group.leave()
//semaphore.signal()
} catch let jsonError {
print(jsonError)
return
}
}).resume()
}
} catch {
print(error.localizedDescription)
}
// Wait to async task to finish before moving on
//_ = semaphore.wait(timeout: DispatchTime.distantFuture)
print("Step 3 Done")
}
}
}