NSURLCache Alamofire removing cached responses - ios

Question

I'm using the following code to test a behavior in NSURLCache. I initialize an API instance in AppDelegate. I configure the manager according to Alamofire's documentation, I configure the shared cache, and I assign dataTaskWillCacheResponse to make sure that the response will indeed be cached.
Then I call makeRequest which checks if a cached response exists (which it shouldn't on the first launch) and then I use my manager to make a request using the same URL so that the request is equivalent throughout the test.
My breakpoint at dataTaskWillCacheResponse is hit, I continue, the responseJSON block is executed and is Successful so I performTests using the request.
First, I check if the response is cached. It is: good!
Second, (and this is the problem) I remove the cached response for that request and then check if it exists. It does: bad!
Third, I check if removing all cached responses will remove that response. It does: good! But it's odd that that worked and the previous attempt at just removing the single response didn't...
Here's the code:
import Alamofire
class API: Manager.SessionDelegate {
var manager: Manager!
override init() {
super.init()
manager = Manager(session: urlSession(), delegate: self)
configureCache(memoryCapacityMB: 5, diskCapacityMB: 25)
manager.delegate.dataTaskWillCacheResponse = { urlSession, dataTask, cachedResponse in
// Placing a breakpoint here confirms that the response is going to be cached
return cachedResponse
}
}
private func urlSession() -> NSURLSession {
let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
return NSURLSession(configuration: configuration, delegate: self, delegateQueue: nil)
}
private func configureCache(memoryCapacityMB memory: Int, diskCapacityMB disk: Int) {
let memoryCapacity = memory * 1024 * 1024
let diskCapacity = disk * 1024 * 1024
let sharedCache = NSURLCache(memoryCapacity: memoryCapacity, diskCapacity: diskCapacity, diskPath: nil)
NSURLCache.setSharedURLCache(sharedCache)
}
// MARK: Request
func makeRequest() {
// The response should be nil on the first launch since nothing has been cached
let request = NSURLRequest(URL: NSURL(string: "http://jsonplaceholder.typicode.com/posts")!)
let response = NSURLCache.sharedURLCache().cachedResponseForRequest(request)
print(response)
manager.request(.GET, request.URLString).responseJSON { response in
switch response.result {
case .Success:
self.performTests(with: response.request!)
case .Failure:
break
}
}
}
func performTests(with request: NSURLRequest) {
// Should exist
var response = NSURLCache.sharedURLCache().cachedResponseForRequest(request)
print(response)
// And it does: good!
// Remove the cached resopnse and check if it exists
NSURLCache.sharedURLCache().removeCachedResponseForRequest(request)
response = NSURLCache.sharedURLCache().cachedResponseForRequest(request)
print(response)
// And it does: bad!
// Try removing all cached responses and check if it exists
NSURLCache.sharedURLCache().removeAllCachedResponses()
response = NSURLCache.sharedURLCache().cachedResponseForRequest(request)
print(response)
// And it doesn't: good! But odd...
}
}
So how does one remove the cached response of a single request then? And is this unintended behavior? Or is NSURLCache behaving correctly and I'm just missing something? Thanks ahead of time for taking a look!

Answer 1

My recollection is that most URL cache changes are not synchronous. They only actually happen after you return to the run loop and allow various asynchronous callbacks to occur.
Try running the rest of the code asynchronously after a delay of 3-5 seconds and see if the request has been removed.
If that doesn't fix the problem, file a bug.