How to prevent EVURLCache to cache a request with Cache-Control header? - ios

Question

I'm using EVURLCache and the POST request response is cached even if cache-control and Pragma headers are defined :
Headers: [
Access-Control-Allow-Headers : Content-Type, Accept, X-Requested-With, remember-me, x-auth-token
Content-Type : application/json;charset=UTF-8
Access-Control-Max-Age : 3600
Cache-Control : no-cache, no-store, max-age=0, must-revalidate
Server : nginx/1.9.15
Connection : keep-alive
Transfer-Encoding : Identity
X-XSS-Protection : 1; mode=block
X-Content-Type-Options : nosniff
Expires : 0
X-Application-Context : application:dev,docker:8080
Pragma : no-cache
Access-Control-Allow-Methods : POST, GET, OPTIONS, DELETE, PUT
Date : Thu, 18 Aug 2016 13:57:15 GMT
Access-Control-Allow-Origin : *
Access-Control-Allow-Credentials : true
]
How to force EVURLCache not to cache such a request ?
I'm initializing cache in my app delegate using the following code:
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// configuring cache
EVURLCache.LOGGING = true // We want to see all caching actions
EVURLCache.activate()
return true
}
Note that I know filters but I wonder if we can just tell it to follow the response header suggested cache behavior

Answer 1

I have created an update (not yet pushed to GitHub) and would like to have your input. The code for the fix for this is:
var shouldSkipCache: String? = nil
// check if caching is allowed according to the request
if request.cachePolicy == NSURLRequestCachePolicy.ReloadIgnoringCacheData {
shouldSkipCache = "request cache policy"
}
// check if caching is allowed according to the response Cache-Control or Pragma header
if let httpResponse = cachedResponse.response as? NSHTTPURLResponse {
if let cacheControl = httpResponse.allHeaderFields["Cache-Control"] as? String {
if cacheControl.lowercaseString.containsString("no-cache") || cacheControl.lowercaseString.containsString("no-store") {
shouldSkipCache = "response cache control"
}
}
if let cacheControl = httpResponse.allHeaderFields["Pragma"] as? String {
if cacheControl.lowercaseString.containsString("no-cache") {
shouldSkipCache = "response pragma"
}
}
}
if shouldSkipCache != nil {
// If the file is in the PreCache folder, then we do want to save a copy in case we are without internet connection
let storagePath = EVURLCache.storagePathForRequest(request, rootPath: EVURLCache._preCacheDirectory) ?? ""
if !NSFileManager.defaultManager().fileExistsAtPath(storagePath) {
EVURLCache.debugLog("CACHE not storing file, it's not allowed by the \(shouldSkipCache) : \(request.URL)")
return
}
EVURLCache.debugLog("CACHE file in PreCache folder, overriding \(shouldSkipCache) : \(request.URL)")
}
In short this means that:
If the request was created while indicating that cached data should beignored then the response will not be written to the cache
If the response has a Cache-Control header that contains no-cache or no-store then the response will not be written to the cache
If the response has a Pragma header that contains no-cache then the response will not be written to the cache
All above will be ignored if the file is already in the cache. (then at least it should be updated)