在swift中使调用同步

Question

我正在尝试将数据从json文件加载到表视图单元格中，但问题是它加载了一个空单元格，因为检索的数据尚未完成加载。我假设我必须使呼叫同步，但我不确定如何。请帮忙！

class func getTopAppsDataFromItunesWithSuccess(success: ((iTunesData: NSData) -> Void)) {
    //1
    loadDataFromURL(NSURL(string: TopAppURL)!, completion:{(data, error) -> Void in
        //2
        if ((data) != nil) {
        if let urlData = data {
            //3
            success(iTunesData: urlData)
        }
        }
    })
}


class func loadDataFromURL(url: NSURL, completion:(data: NSData?, error: NSError?) -> Void) {
    var session = NSURLSession.sharedSession()

// Use NSURLSession to get data from an NSURL
let loadDataTask = session.dataTaskWithURL(url, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
    if let responseError = error {
        println("error")
        completion(data: nil, error: responseError)
    } else if let httpResponse = response as? NSHTTPURLResponse {

        if httpResponse.statusCode != 200 {
            var statusError = NSError(domain:"com.raywenderlich", code:httpResponse.statusCode, userInfo:[NSLocalizedDescriptionKey : "HTTP status code has unexpected value."])
            completion(data: nil, error: statusError)
        } else {

            completion(data: data, error: nil)
        }
    }
})

loadDataTask.resume()


}

这是我提出请求的地方

class func allCats() -> Array<Animal> {

    var animalArray = Array<Animal>()

       DataManager.getTopAppsDataFromItunesWithSuccess { (iTunesData) -> Void in
...