ios - 具有操作 block 的 NSOperationQueue 在 SWIFT 中未按预期工作

Question

我必须按顺序检查一系列操作。但如果任何操作失败，我需要在执行队列中列出的操作之前调用其他操作。

for example:

priority 1 : Fetch all companies lookups
priority 2 : Fetch all regions
priority 3...N : Fetch all cities individually for each region

在每次操作中我都会传递一把 key ，该 key 仅在 2 小时内有效...假设 key 是在上午 10 点生成的，我将开始从服务器获取数据，需要 15 分钟才能完全获取所有数据。

但问题是我已于上午 11:59 开始获取数据，并且在获取信息期间 key 已过期。所以我需要再发送一个请求来获取 key 并进一步进行下一步操作。

so it looks like:
priority 1 : Fetch all companies lookups with key
priority 2 : Fetch all regions (i.e. 4 Regions available) with key
   priority 3 : Fetch all cities for region 1 with key
   priority 4 : Fetch all cities for region 2 with key (here key is expire) so for taking new key need to add new operation here, which fetch new key which is valid again for next two hours.
   priority 5 : Fetch all cities for region 3 with new key
   priority 6 : Fetch all cities for region 4 with new key

我尝试过的代码:

var queue = NSOperationQueue.mainQueue()
queue.addOperationWithBlock({
  callService(“http://dsn/FetchingCompanyData”)
}

queue.addOperationWithBlock({
  callService(“http://dsn/FetchingRegionData”)
  //get region List here
  for region in regions{
   queue.addOperationWithBlock({
    callService(“http://dsn/FetchingCities?region=\(region.code)”)
    //check in response if response return message like KEY_EXPIRE
    if(error){
      queue.addOperationWithBlock({
        var newKey = callService(“http://dsn/FetchingCities?region=\(region.code)”)
        setKeyToCache(newKey)
      })
    }
  }
}
}

fun callService(urlStr: String){
    let myURL = NSURL(string: urlStr)!
    var key = getKeyFromCache()
    var request = NSMutableURLRequest(URL: myURL)
    var errorHandling = ErrorHandling()
    request.HTTPMethod = "POST"
    request.timeoutInterval = 10000.0
    request.addValue("application/xml", forHTTPHeaderField: "Content-Type")
    request.addValue("application/xml", forHTTPHeaderField: "Accept")
    request.setValue("Basic \(key)", forHTTPHeaderField: "Authorization")

    NSURLConnection.sendAsynchronousRequest(request, queue: queue) { response, data, error in ..}
}

此代码未按预期工作。

它在队列中添加操作如下:

Queue:
Operation 1: Fetch companies
Operation 2: Fetch Regions
Operation 3: Fetch cities for region 1
Operation 4: Fetch cities for region 2
Operation 5: Fetch cities for region 3
Operation 6: Fetch cities for region 4
Operation 7: Fetch new key for region 1
Operation 7: Fetch new key for region 2
Operation 7: Fetch new key for region 3
Operation 7: Fetch new key for region 4

而不是这个，我想要如下的操作顺序。

 Operation 1: Fetch companies
    Operation 2: Fetch Regions
    Operation 3: Fetch cities for region 1
    Operation 4: Fetch cities for region 2
    Operation 5: Fetch new key for region 2
    Operation 6: Again Fetch cities for region 2
    Operation 7: Fetch cities for region 3
    Operation 8: Fetch cities for region 4

任何帮助将不胜感激。

Answer 1

通过添加同步调用而不是异步调用解决了此问题。