变量不断返回nil-Swift iOS

我正在使用Alamofire解析JSON数据。在下面提到的代码中，除了“var id:JSON？”变量之外，其他一切都正常工作，尽管它更新得很好，但在某一点（底部）它一直返回nil。我需要把这个变量放在过滤器闭包中

class GreetingObjectHandler {
    var greetings: [Greeting] = []
    var id: JSON? //this variable
    init(filename: String) {
        Alamofire.request(.GET, "http://localhost:2403/users/me")
            .responseJSON { (req, res, data, error) in
                if(error != nil) {
                    NSLog("Error: \(error)")
                }
                else {
                    var parse = JSON(data!)
                    self.id = parse["id"] //updating 
                    println(self.id) //it's fine here
                }
        }

        let filePath = NSURL(string: "http://localhost:2403/users")
        let jsonData = NSData(contentsOfURL:filePath!)
        let json = JSON(data: jsonData!, options: NSJSONReadingOptions.AllowFragments, error: nil)

        for (key: String, subJson: JSON) in json {

            var language:String?, link: String?, description:String?, greetingText: String?

            for (key1, value:JSON) in subJson {
                switch key1 {
                case "displayName": language = value.string
                case "id": link = value.string
                case "username": description = value.string
                case "mainSkill": greetingText = value.string
                default: break
                }
            }

            let greeting = Greeting(language: language, link: link, description: description, greetingText: greetingText)
            self.greetings.append(greeting)
            self.greetings = self.greetings.filter { $0.link != "\(self.id)"} //this filter
         println(self.id)   //returns nil
        }
    }

    func getGreetingsAsAnyObjects() -> [String: [AnyObject]]{

        return [Constant.GreetingOBJHandlerSectionKey: greetings.map { $0 as AnyObject }]
    }
}

---

Alamofire请求异步运行，因此init函数末尾的

println

语句在

responseJSON

闭包末尾的

println

语句之前运行。解决方法是运行需要

responseJSON

闭包中的

json

变量的代码。

虽然人们的评论很好地解释了您的问题所在，但我认为应该使用闭包创建一个函数来处理您的请求，然后在完成处理程序中处理其余部分可以帮助您组织代码，如下所示：

func getJSON(url: String, completionHandler: (json: JSON?, error: NSError?) -> ()) {

    Alamofire.request(.GET, url)
        .responseJSON { (req, res, data, error) in completionHandler(
            json: {

                if let d = data {
                    var parse = JSON(d)
                    return parse
                }

                return nil
            }(), error: error)
    }
}

init(filename: String) {

    self.getJSON("http://localhost:2403/users") { json, error in
        if(error != nil) {
            NSLog("Error: \(error)")
        }
        else {
            self.id = json["id"]

            let filePath = NSURL(string: "http://localhost:2403/users")
            let jsonData = NSData(contentsOfURL:filePath!)
            let json = JSON(data: jsonData!, options: NSJSONReadingOptions.AllowFragments, error: nil)

            for (key: String, subJson: JSON) in json {

              var language:String?, link: String?, description:String?, greetingText: String?

              for (key1, value:JSON) in subJson {
                switch key1 {
                case "displayName": language = value.string
                case "id": link = value.string
                case "username": description = value.string
                case "mainSkill": greetingText = value.string
                default: break
              }
            }

            let greeting = Greeting(language: language, link: link, description: description, greetingText: greetingText)
            self.greetings.append(greeting)
            self.greetings = self.greetings.filter { $0.link != "\(self.id)"} //this filter
            println(self.id)
        }
    }
} 

然后您可以通过以下方式调用

init

：

func getJSON(url: String, completionHandler: (json: JSON?, error: NSError?) -> ()) {

    Alamofire.request(.GET, url)
        .responseJSON { (req, res, data, error) in completionHandler(
            json: {

                if let d = data {
                    var parse = JSON(d)
                    return parse
                }

                return nil
            }(), error: error)
    }
}

init(filename: String) {

    self.getJSON("http://localhost:2403/users") { json, error in
        if(error != nil) {
            NSLog("Error: \(error)")
        }
        else {
            self.id = json["id"]

            let filePath = NSURL(string: "http://localhost:2403/users")
            let jsonData = NSData(contentsOfURL:filePath!)
            let json = JSON(data: jsonData!, options: NSJSONReadingOptions.AllowFragments, error: nil)

            for (key: String, subJson: JSON) in json {

              var language:String?, link: String?, description:String?, greetingText: String?

              for (key1, value:JSON) in subJson {
                switch key1 {
                case "displayName": language = value.string
                case "id": link = value.string
                case "username": description = value.string
                case "mainSkill": greetingText = value.string
                default: break
              }
            }

            let greeting = Greeting(language: language, link: link, description: description, greetingText: greetingText)
            self.greetings.append(greeting)
            self.greetings = self.greetings.filter { $0.link != "\(self.id)"} //this filter
            println(self.id)
        }
    }
} 

使用上面的代码，您可以使用闭包来确保您的请求已完成

---

我希望这对你有所帮助。

你所有的建议都是有效的，但这才是真正有效的

import Foundation
import Alamofire

class GreetingObjectHandler {
    var greetings: [Greeting] = []

    init(filename: String) {

        let fileP = NSURL(string: "http://localhost:2403/users/me")
        let jsonD = NSData(contentsOfURL:fileP!)
        let jso = JSON(data: jsonD!, options: NSJSONReadingOptions.AllowFragments, error: nil)
        var id = jso["id"]


        let filePath = NSURL(string: "http://localhost:2403/users")
        let jsonData = NSData(contentsOfURL:filePath!)
        let json = JSON(data: jsonData!, options: NSJSONReadingOptions.AllowFragments, error: nil)

        for (key: String, subJson: JSON) in json {

            var language:String?, link: String?, description:String?, greetingText: String?

            for (key1, value:JSON) in subJson {
                switch key1 {
                case "displayName": language = value.string
                case "id": link = value.string
                case "username": description = value.string
                case "mainSkill": greetingText = value.string
                default: break
                }
            }

            let greeting = Greeting(language: language, link: link, description: description, greetingText: greetingText)
            self.greetings.append(greeting)
            self.greetings = self.greetings.filter { $0.link != "\(id)"}
        }
    }

    func getGreetingsAsAnyObjects() -> [String: [AnyObject]]{

        return [Constant.GreetingOBJHandlerSectionKey: greetings.map { $0 as AnyObject }]
    }
}

---

request（）是一个异步操作。如果不添加诸如println（“1（self.if）”）之类的内容，就无法知道首先调用哪一行。它返回nil，因为它在主线程上运行，请求操作尚未成功完成，无法为id属性赋值。它没有通过。@SatnamSync“它没有通过”是什么意思