我遇到的问题是应该从dropbox返回加密文件的函数，而是返回我初始化的空字典以接收数据。
我几乎可以肯定这是一个竞争条件问题，因为必须对Dropbox API进行异步调用，但到目前为止我一直无法使用GCD解决问题。任何帮助都将非常感激：
func loadDropboxAccounts() {
let retreiveDataGroup = dispatch_group_create()
var dictionary = [String:String]()
dispatch_group_enter(retreiveDataGroup)
if DropboxClientsManager.authorizedClient() == nil {
DropboxClientsManager.authorizeFromController(UIApplication.sharedApplication(), controller: self, openURL: {(url: NSURL) -> Void in
UIApplication.sharedApplication().openURL(url)
}, browserAuth: true)
}
if let client = DropboxClientsManager.authorizedClient() {
client.filesRoutes.downloadData("/example/example.txt").response({(result: AnyObject?, routeError: AnyObject?, error: DBError?, fileContents: NSData) -> Void in
if (fileContents.length != 0) {
let cipherTextData = fileContents
let plainTextByteArray = CryptoHelper.accountDecrypt(cipherTextData, fileName: "vault")
let plainTextString = plainTextByteArray.reduce("") { $0 + String(UnicodeScalar($1)) }
let plainTextData = dataFromByteArray(plainTextByteArray)
do {
try dictionary = NSJSONSerialization.JSONObjectWithData(plainTextData, options: []) as! [String:String]
for (key, value) in dictionary {
let t = dictionary[key]
print(t)
}
} catch let error as NSError{
print("loadAccountInfo:", error)
}
} else {
print("\(routeError)\n\(error)\n")
}
}).progress({(bytesDownloaded: Int64, totalBytesDownloaded: Int64, totalBytesExpectedToDownload: Int64) -> Void in
print("\(bytesDownloaded)\n\(totalBytesDownloaded)\n\(totalBytesExpectedToDownload)\n")
})
}
dispatch_group_notify(retreiveDataGroup, dispatch_get_main_queue()) {
return dictionary
}
}
仅供参考，这是我在项目中使用的pod：