使用字典和字典数组进行Swift JSON解析

Question

我是使用Swift语言进行iOS开发的初学者。我有一个包含以下数据的JSON文件。

{
    "success": true,
    "data": [
             {
                 "type": 0,
                 "name": "Money Extension",
                 "bal": "72 $",
                 "Name": "LK_Mor",
                 "code": "LK_Mor",
                 "class": "0",
                 "withdraw": "300 $",
                 "initval": "1000 $"
             },
             {

             },
             {

             },
             ]
}

我想解析此文件，并且必须返回包含JSON文件中数据的字典。这是我写的方法。

enum JSONError: String, ErrorType {
    case NoData = "ERROR: no data"
    case ConversionFailed = "ERROR: conversion from JSON failed"
}

func jsonParserForDataUsage(urlForData:String)->NSDictionary{
    var dicOfParsedData :NSDictionary!
    print("json parser activated")
    let urlPath = urlForData
    let endpoint = NSURL(string: urlPath)
    let request = NSMutableURLRequest(URL:endpoint!)
            NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
                do {

                    guard let dat = data else {
                        throw JSONError.NoData
                    }
                    guard let dictionary: NSDictionary = try NSJSONSerialization.JSONObjectWithData(dat, options:.AllowFragments) as? NSDictionary else {
                        throw JSONError.ConversionFailed
                    }

                    print(dictionary)
                    dicOfParsedData = dictionary

                } catch let error as JSONError {
                    print(error.rawValue)
                } catch {
                    print(error)
                }
                }.resume()

          return dicOfParsedData

}

当我修改此方法以返回字典时，它总是返回nil。如何修改此方法。

Answer 1

您不能return执行异步任务。您必须改用回调。

添加这样的回调：

completion: (dictionary: NSDictionary) -> Void

解析器方法签名：

func jsonParserForDataUsage(urlForData: String, completion: (dictionary: NSDictionary) -> Void)

并在您要“返回”的数据可用的地方调用补全：

func jsonParserForDataUsage(urlForData: String, completion: (dictionary: NSDictionary) -> Void) {
    print("json parser activated")
    let urlPath = urlForData
    guard let endpoint = NSURL(string: urlPath) else {
        return
    }
    let request = NSMutableURLRequest(URL:endpoint)
    NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
        do {

            guard let dat = data else {
                throw JSONError.NoData
            }
            guard let dictionary = try NSJSONSerialization.JSONObjectWithData(dat, options:.AllowFragments) as? NSDictionary else {
                throw JSONError.ConversionFailed
            }

            completion(dictionary: dictionary)

        } catch let error as JSONError {
            print(error.rawValue)
        } catch let error as NSError {
            print(error.debugDescription)
        }
    }.resume()

}

现在，您可以将此方法与结尾的闭包一起使用，以获取“返回的”值：

jsonParserForDataUsage("http...") { (dictionary) in
    print(dictionary)
}