Download image directly to a photo album - ios

Question

Currently I'm using Alamofire for network requests. How can I download an image directly to a photo album that already exists using the PHPhotoLibrary from Photos.framework?
P.S.: I don't mind to have a solution using NSURLSession by itself.
Considerations: The file can't be stored in disk temporarily. I want the data in memory and save it once into the disk using the Photos.framework.

Answer 1

I figure it out by myself. I implemented it with a dataTaskWithRequest from NSURLSession.
Initially I thought using the NSData(contentsOfURL:) but the contentsOfURL method does not return until the entire file is transferred. It should only be used for local files and not for remote ones because if you're loading a large content and the device has a slow connection then the UI will be blocked.
// Avoid this!
let originalPhotoData = NSData(contentsOfURL: NSURL(string: "http://photo.jpg")!)
So, it is possible to load the content into a NSData with a data task. One solution can be like:
let request = NSMutableURLRequest(URL: NSURL(string: urlString.URLString)!)
request.allHTTPHeaderFields = [
"Content-Type": "image/jpeg"
]
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { data, response, error in
if let e = error {
print(e.description)
return
}
guard let image = UIImage(data: data) else {
print("No image")
return
}
// Success
// Note: does not save into an album. I removed that code to be more concise.
PHPhotoLibrary.sharedPhotoLibrary().performChanges {
let creationRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
}, completionHandler: { (success : Bool, error : NSError?) -> Void in
if success == false, let e = error){
print(e)
}
}
}
task.resume()
The data is only available in the final stage but you can instead access the data and see the progress using a session delegate.
class Session: NSObject, NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate {
let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
let queue = NSOperationQueue.mainQueue()
var session = NSURLSession()
var buffer = NSMutableData()
var expectedContentLength = 0
override init() {
super.init()
session = NSURLSession(configuration: configuration, delegate: self, delegateQueue: queue)
}
func dataTaskWithRequest(request: NSURLRequest) -> NSURLSessionDataTask {
// The delegate is only called if you do not specify a completion block!
return session.dataTaskWithRequest(request)
}
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveResponse response: NSURLResponse, completionHandler: (NSURLSessionResponseDisposition) -> Void) {
buffer = NSMutableData()
expectedContentLength = Int(response.expectedContentLength)
print("Expected content length:", expectedContentLength)
completionHandler(NSURLSessionResponseDisposition.Allow)
}
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) {
buffer.appendData(data)
let percentageDownloaded = Float(buffer.length) / Float(expectedContentLength)
print("Progress: ", percentageDownloaded)
}
func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) {
print("Finished with/without error \(error)")
// Use the buffer to create the UIImage
}
}