NSURL Connection cache data for offine app - iphone

Question

I have to develop a application for i iphone which can work in two way one is on line other is offline.When there is internet it should show the data from the network but when there is no network it needed to show cached data.I am using nsurl connection for getting data from server.My code is following
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:strUrl]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSURLConnection *conn = [NSURLConnection connectionWithRequest:request
delegate:self];
[conn start];
also the delegate which is not getting called as well
-(NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:
(NSCachedURLResponse *)cachedResponse
{
return cachedResponse;
}
can anyone please guide me how to get data stored in cache in NSURLConnection in ios..Thanks in advance.:)

Answer 1

Sorry for delay u need to do some research on this :)
hope this will helps u
i tried by downloading the image i will get it even in the offline.
just go throught this may be helps u :)
in app delegate set the create cache
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// Override point for customization after application launch.
self.viewController = [[[ViewController alloc] initWithNibName:#"ViewController" bundle:nil] autorelease];
//need to add this
NSURLCache *URLCache = [[NSURLCache alloc] initWithMemoryCapacity:4 * 1024 * 1024
diskCapacity:20 * 1024 * 1024
diskPath:nil];
[NSURLCache setSharedURLCache:URLCache];
// set sharedcache
self.window.rootViewController = self.viewController;
[self.window makeKeyAndVisible];
return YES;
}
//in your downloading view controller
#import "ViewController.h"
#interface ViewController ()<NSURLConnectionDelegate> // confirms to this delegate
{
NSMutableData *imagData;
}
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSURL *url = [NSURL URLWithString:#"http://static.adzerk.net/Advertisers/d9a919813dac42adbd0e3106bc19bc04.png"];
NSURLRequest *Req = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];
NSURLConnection *conn = [NSURLConnection connectionWithRequest:Req delegate:self];
if(conn == nil)
{
conn = nil;
[conn cancel];
}
}
- (void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data
{
if(imagData == nil)
{
imagData = [[NSMutableData alloc]init];
}
// NSURLResponse *resp = [[NSURLResponse alloc]initWithURL:[NSURL URLWithString:#"http://static.adzerk.net/Advertisers/d9a919813dac42adbd0e3106bc19bc04.png"] MIMEType:#"" expectedContentLength:50 textEncodingName:#"image"];
// NSLog(#"%#",connection.description);
// NSLog(#"%#",resp.description);
//
// NSCachedURLResponse *chacheResp = [[NSCachedURLResponse alloc]initWithResponse:resp data:data];
//
[imagData appendData:data];
UIImage *aimage=[[UIImage alloc]initWithData:imagData];
self.aview.image = aimage;
}
-(NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
NSMutableDictionary *userInfo = [[cachedResponse userInfo] mutableCopy];
NSMutableData *mutData = [[cachedResponse data] mutableCopy];
NSURLCacheStoragePolicy storagePolicy = NSURLCacheStorageAllowedInMemoryOnly;
return [[NSCachedURLResponse alloc] initWithResponse:[cachedResponse response]
data:mutData
userInfo:userInfo
storagePolicy:storagePolicy];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
connection = nil;
[connection cancel];
}
and also go through link provided by AdamG

Answer 2

You need to make sure to allocate the cache in applicationDidFinishLaunching:
This is the code you need to do that:
NSURLCache *URLCache = [[NSURLCache alloc] initWithMemoryCapacity:4 * 1024 * 1024
diskCapacity:20 * 1024 * 1024
diskPath:nil];
[NSURLCache setSharedURLCache:URLCache];
And the caching code should also look different:
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
NSMutableDictionary *mutableUserInfo = [[cachedResponse userInfo] mutableCopy];
NSMutableData *mutableData = [[cachedResponse data] mutableCopy];
NSURLCacheStoragePolicy storagePolicy = NSURLCacheStorageAllowedInMemoryOnly;
// ...
return [[NSCachedURLResponse alloc] initWithResponse:[cachedResponse response]
data:mutableData
userInfo:mutableUserInfo
storagePolicy:storagePolicy];
}
For more see http://www.nshipster.com/nsurlcache/ but that should probably fix your problem.