观察asynchronous请求

我有三个独立的API调用。 当所有三个调用完成后，我将汇总数据并使用它来形成一个单独的模型对象。

我想我会用财产观察员来做到这一点，但我不知道它将如何实施。 任何帮助或指导将不胜感激。

我创build了一个模型对象来进行networking调用，将响应数据传递给一个转义闭包。 这是parsing数据的function：

func loadLibrary() { // League Data Containers var names = Dictionary<Int, String>() // API Call 1 var titles = Dictionary<Int, String>() // Call 1 var masteryLevels = Dictionary<Int, Int>() // 2 var masteryPoints = Dictionary<Int, Int>() // 2 // Champion Data Containers var championRolesLibrary = Array<Dictionary<String,Array<Role>>>() // 3 var championWithRoles = Dictionary<String,Array<Role>>() // 3 var championRoles = Array<Role>() // 3 // Making Calls to the APIs leagueAPI.downloadStaticData { data in // API Call is made and data is parsed into containers } leagueAPI.downloadChampionMasteryData { data in // API Call is made and data is parsed into containers } championAPI.downloadChampionRolesData { data in // API Call is made and data is parsed into containers } // Once all three calls have completed and the data has been parsed into different containers, the data is all brought together to create a library of objects. func aggregateData() { // Take data from all the containers and use them in here. // The issue is when to call this function. } } 

Answer 1

解决这个问题的一个简单的方法是嵌套所有三个请求：

 func loadLibrary() { // League Data Containers var names = Dictionary<Int, String>() // API Call 1 var titles = Dictionary<Int, String>() // Call 1 var masteryLevels = Dictionary<Int, Int>() // 2 var masteryPoints = Dictionary<Int, Int>() // 2 // Champion Data Containers var championRolesLibrary = Array<Dictionary<String,Array<Role>>>() // 3 var championWithRoles = Dictionary<String,Array<Role>>() // 3 var championRoles = Array<Role>() // 3 // Making Calls to the APIs leagueAPI.downloadStaticData { data in // API Call is made and data is parsed into containers leagueAPI.downloadChampionMasteryData { data2 in // API Call is made and data is parsed into containers championAPI.downloadChampionRolesData { data3 in // API Call is made and data is parsed into containers// Once all three calls have completed and the data has been parsed into different containers, the data is all brought together to create a library of objects. aggregateData() { // Take data from all the containers and use them in here. // The issue is when to call this function. } } } } } 

---

编辑：你也可以使用DispatchGroup完成你想要的@ rmaddy所说的，在这种情况下你可以这样做：

 func loadLibrary() { // League Data Containers var names = Dictionary<Int, String>() // API Call 1 var titles = Dictionary<Int, String>() // Call 1 var masteryLevels = Dictionary<Int, Int>() // 2 var masteryPoints = Dictionary<Int, Int>() // 2 // Champion Data Containers var championRolesLibrary = Array<Dictionary<String,Array<Role>>>() // 3 var championWithRoles = Dictionary<String,Array<Role>>() // 3 var championRoles = Array<Role>() // 3 // Create DispatchGroup let dispatchGroup = DispatchGroup() // Making Calls to the APIs dispatchGroup.enter() leagueAPI.downloadStaticData { data in // API Call is made and data is parsed into containers dispatchGroup.leave() } dispatchGroup.enter() leagueAPI.downloadChampionMasteryData { data in // API Call is made and data is parsed into containers dispatchGroup.leave() } dispatchGroup.enter() championAPI.downloadChampionRolesData { data in // API Call is made and data is parsed into containers dispatchGroup.leave() } // Once all three calls have completed and the data has been parsed into different containers, the data is all brought together to create a library of objects. dispatchGroup.notify(queue: DispatchQueue.global(qos: .background)){ aggregateData() { // Take data from all the containers and use them in here. // The issue is when to call this function. } } }