如何使用 NSURL 等待异步请求完成？

Question

我曾尝试将此代码转换为使用“sendSynchronousRequest()”，但没有成功，因为 SO 上的大多数资源都已过时。

我正在尝试从 API 收集数据。然后它用我需要的信息创建了一个 Marvel Characters 数组。整个代码工作正常，但数组是空的，因为它 returns 请求完成之前的数据。如何等待数据？

static func getCharacters() -> Array<MarvelCharModel>{
    var CharactersFromApi = [MarvelCharModel]();

    let baseUrl = "https://gateway.marvel.com";
    let charUri = "/v1/public/characters";
    let apiKey  = "apikey=xxxxxxxxxxxxxxxxxxxx";

    let url = URL(string: baseUrl + charUri + "?" + apiKey)!

    var response: URLResponse?

    var request = URLRequest(url: url)
    request.httpMethod = "GET"
    request.addValue("developer.marvel.com", forHTTPHeaderField: "Referer")

    NSURLConnection.sendAsynchronousRequest(request, queue: OperationQueue.main) {(response, data, error) in
        guard let data = data else { return }

        let responseJSON = try? JSONSerialization.jsonObject(with: data, options: [])
        if let responseJSON = responseJSON as? [String: Any] {
            if let dataInfo = responseJSON["data"] as? [String: Any] {
                let results = dataInfo["results"] as! NSArray;
                for dataCharacter in results {

                    let character = dataCharacter as? [String: Any];
                    let charId = character?["id"] as! Int;
                    let charName = character?["name"] as! String;
                    let charDesc = character?["description"] as! String;
                    let charPic = character?["thumbnail"] as! [String: Any];
                    let charPath = charPic["path"] as! String;
                    let charExt = charPic["extension"] as! String;

                    CharactersFromApi.append(MarvelCharModel(name: charName, desc: charDesc, pic: charPath + "." + charExt, id: charId));

                    // print(CharactersFromApi) <-- This shows correctly but clearly the return at the bottom is not waiting
                }

            }
        }
    }

    return getFavourite(characters: CharactersFromApi); // CharactersFromAPI is empty
}

Answer 1

你必须等到所有接收到的数据都没有附加到本地数组，然后你必须调用完成。

因此，不用 return 类型，而是在参数

中添加完成处理程序

static func getCharacters(_ completion: @escaping ([MarvelCharModel]) -> () )

然后在 foreach 循环调用之后 completion

for dataCharacter in results {
    ...
}
completion(getFavourite(characters: CharactersFromApi))

然后你可以调用这个方法，你可以在它的闭包中访问 received MarvelCharModel

Foo.getCharacters { characters in
    ... // do what you need when completion is called 
}

如何使用 NSURL 等待异步请求完成？

How can I wait for an asynchronous request to finish using NSURL?

ios

swift

swift4