swift - 在方法A中，在方法B中从回调中获取数据？

Question

我有一个构建函数，用于从 API 获取最新项目。还有其他几个，具有不同的功能，但它们的工作原理都是一样的。它看起来像这样:

func getLatest(pageNumber: Int) -> Array<Any>{
    let urlRequest = URL(string: baseUrl + latestUrl + String(pageNumber))

    let requestedData = doRequest(url: urlRequest!, completion: { data -> Void in
        // We have the data from doRequest stored in data, but now what?!

    })

    return allData
}

我还有一个处理请求的异步方法。那个看起来像这样:

func doRequest(url: URL, completion: @escaping ([[ApiItem]]) -> ()){
    var allItems = [[ApiItem]]()

    URLSession.shared.dataTask(with: url) { (data, response, error) in
        guard let data = data else { return }

        do{
            let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! [String: AnyObject]

            let results = json["items"] as? [AnyObject]

            for r in results!{
                let item = ApiItem(json: r as! [String: Any])

                allItems.append([item])
            }

            completion(allItems)
        } catch let jsonError{
            print("JSON error: \(jsonError)")
        }
    }.resume()

doRequest 函数工作得非常好。它获取数据，解析 JSON 并将其发送回 getLatest --> requestedData。现在的问题是，getLatest() 是一个函数，需要 返回存储在 data 变量中的数据 requestedData.

我怎样才能使 getLatest() 函数返回存储在 requestedData() 中的 data 中的数据？

Answer 1

所以我通过这样做修复了它:

在第一种方法中，实际上需要来自 API 的数据，我添加了这个:

let trendingData = restApiManager.getLatest(pageNumber: 0, completion: { data -> Void in
   let item = data[indexPath.row]

   let url = NSURL(string: item.still)

   let data = NSData(contentsOf: url as! URL)
   if data != nil {
       cell.image.image = UIImage(data:data! as Data)
   }             
})

getLatest() 方法如下所示:

func getLatest(pageNumber: Int, completion: @escaping ([ApiItem]) -> ()) {
    let urlRequest = URL(string: baseUrl + trendingUrl + String(pageNumber))

    let requestedData = doRequest(url: urlRequest!, completion: { data -> Void in
        // We have the data from doRequest stored in data
        var requestedData = data
        completion(requestedData)
    })
}

最后，doRequest() 方法如下所示:

func doRequest(url: URL, completion: @escaping ([ApiItem]) -> ()){
    var allItems = [ApiItem]()

    URLSession.shared.dataTask(with: url) { (data, response, error) in
        guard let data = data else { return }

        do{
            let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! [String: AnyObject]

            let results = json["items"] as? [AnyObject]

            for r in results!{
                let item = ApiItem(json: r as! [String: Any])

                allItems.append(item)
            }

            completion(allItems)
        } catch let jsonError{
            print("JSON error: \(jsonError)")
        }
    }.resume()
}