So i'm having hard time understanding something. This are the things i understand about NSURSession :
所以我很难理解一些东西。这是我对NSURSession的理解:
-
Generally , I have 2 options for (as far as i know) DataTask(e.x dataTaskWithRequest) And DownloadTask(e.x DownloadTaskWithRequest) - Using thier delegate method , or use the completion handler , Cant do both. I have managed to receive DATA using dataTaskWithRequest like this :
一般来说，我有两个选项(据我所知)DataTask(e)。x dataTaskWithRequest)和DownloadTask(e。使用它们的委托方法，或者使用完成处理程序，这两种方法都不行。我已经设法使用dataTaskWithRequest来接收数据，如下所示:
let request = NSMutableURLRequest(URL: dataSourceURL!) request.HTTPMethod = "POST" let postString = "lastid=\(id)" request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding) let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { data, response, error in if error != nil { println("error=\(error)") return } if data != nil { println("works") //Handle data } //println("response = \(response)") } task.resume()
It works perfectly. The problem is that i need to DOWNLOAD the data to the disk and not only to the memory(I'm downloading images). So i tried the same with DownloadTaskWithRequest + his completion handler and i have noticed that the parameters he takes are the same expect the first one which is NSURL and in DataTaskWithRequest is NSData so it makes things very simpler. e.X
它的工作原理。问题是，我需要将数据下载到磁盘中，而不是只下载到内存中(我正在下载图像)。我对DownloadTaskWithRequest +他的完成处理器也做了同样的尝试，我注意到他接受的参数都是一样的，第一个是NSURL，在DataTaskWithRequest中是NSData，这让事情变得非常简单。e.X
let task2 = NSURLSession.sharedSession().downloadTaskWithRequest(request, completionHandler: { (location : NSURL!, response : NSURLResponse!, error : NSError?) -> Void in
if error != nil {
return
}
//How do i get the data??
})
task2.resume()
My Question is this : I know i can fetch the DATA out of the Location(NSURL) using :
我的问题是:我知道我可以使用以下方法从该位置(NSURL)获取数据:
var data = NSData(contentsOfURL: location)
1)Will contentsOfURL will make another "request" do get this data , or that he is working locally? If it sending request again , how can i avoid it?
1) contentsOfURL是否会发出另一个“请求”来获取这些数据，还是他在本地工作?如果它再次发送请求，我如何避免它?
2)Is this the right way(I know i can use the delegate methods, I prefer not)?
2)这是正确的方法吗(我知道我可以使用委托方法，我不喜欢)?
3)How can i store the data i have downloaded(after questions number 1 and 2 answered) locally , and access it if needed?
3)如何将下载的数据(在问题1和问题2回答后)存储在本地，并在需要时进行访问?
Thank you guys!! Sorry for newibie question , I really do care about efficient - Thank you!
谢谢你们! !不好意思，newibie的问题，我真的很关心效率-谢谢!
1 个解决方案
#1
14
When using download tasks, generally one would simply use the location provided by the completionHandler of the download task to simply move the file from its temporary location to a final location of your choosing (e.g. to the Documents or Cache folder) using NSFileManager.
使用下载任务时，通常只需使用下载任务的completionHandler提供的位置，使用NSFileManager将文件从临时位置移动到您选择的最终位置(例如，到文档或缓存文件夹)。
let task = NSURLSession.sharedSession().downloadTaskWithURL(url) { location, response, error in
guard location != nil && error == nil else {
print(error)
return
}
let fileManager = NSFileManager.defaultManager()
let documents = try! fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
let fileURL = documents.URLByAppendingPathComponent("test.jpg")
do {
try fileManager.moveItemAtURL(location!, toURL: fileURL)
} catch {
print(error)
}
}
task.resume()
You certainly could also load the object into a NSData using contentsOfURL. Yes, it works with local resources. And, no, it won't make another request ... if you look at the URL it is a file URL in your local file system. But you lose much of the memory savings of download tasks that way, so you might use a data task if you really wanted to get it into a NSData. But if you wanted to move it to persistent storage, the above pattern probably makes sense, avoiding using a NSData object altogether.
当然，也可以使用contentsOfURL将对象加载到NSData中。是的，它与当地资源一起工作。而且，不，它不会再提出要求……如果查看URL，它是本地文件系统中的文件URL。但是这样你就失去了下载任务的大部分内存节省，所以如果你真的想把数据任务放到NSData中，你可以使用它。但是，如果您想将它移动到持久存储，那么上面的模式可能是有意义的，避免使用NSData对象。
#1
14
When using download tasks, generally one would simply use the location provided by the completionHandler of the download task to simply move the file from its temporary location to a final location of your choosing (e.g. to the Documents or Cache folder) using NSFileManager.
使用下载任务时，通常只需使用下载任务的completionHandler提供的位置，使用NSFileManager将文件从临时位置移动到您选择的最终位置(例如，到文档或缓存文件夹)。
let task = NSURLSession.sharedSession().downloadTaskWithURL(url) { location, response, error in
guard location != nil && error == nil else {
print(error)
return
}
let fileManager = NSFileManager.defaultManager()
let documents = try! fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
let fileURL = documents.URLByAppendingPathComponent("test.jpg")
do {
try fileManager.moveItemAtURL(location!, toURL: fileURL)
} catch {
print(error)
}
}
task.resume()
You certainly could also load the object into a NSData using contentsOfURL. Yes, it works with local resources. And, no, it won't make another request ... if you look at the URL it is a file URL in your local file system. But you lose much of the memory savings of download tasks that way, so you might use a data task if you really wanted to get it into a NSData. But if you wanted to move it to persistent storage, the above pattern probably makes sense, avoiding using a NSData object altogether.
当然，也可以使用contentsOfURL将对象加载到NSData中。是的，它与当地资源一起工作。而且，不，它不会再提出要求……如果查看URL，它是本地文件系统中的文件URL。但是这样你就失去了下载任务的大部分内存节省，所以如果你真的想把数据任务放到NSData中，你可以使用它。但是，如果您想将它移动到持久存储，那么上面的模式可能是有意义的，避免使用NSData对象。