我是使用Swift语言进行iOS开发的初学者。我有一个JSON文件，其中包含以下数据。
{
"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。
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)
}
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