load data from cache with NSURL doesn't work - objective-c

Question

i'm trying to load a photo from my cache directory.
this is the code where i write the photo into a cache folder:
+(BOOL)writeAData:(NSData *)imageData atURL:(NSURL *)fileUrl
{
return [imageData writeToURL:fileUrl atomically:YES];
}
this code works fine, but i have problems when i try to load the code from the cache folders:
i use the method initWithContentsOfURL inside a block:
NSData *imageData = [[NSData alloc] initWithContentsOfURL:self.imageUrl];
this is the format of url
file://localhost/Users/MarcoMignano/Library/Application%20Support/iPhone%20Simulator/6.1/Applications/0E8E54D8-9634-41CF-934B-A7315411F12F/Library/Caches/image_cache/Meyer%20Library.jpg
the URL is correct, but when i try to use the method above i get this error:
..... [__NSCFString isFileURL]: unrecognized selector sent to instance 0x8a0c5b0 .....
that is the code when i take the url of my model:
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:YES];
self.photos = [PhotoAlreadyDisplayed getAllPicture];
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([sender isKindOfClass:[UITableViewCell class]]) {
NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
if (indexPath) {
if ([segue.identifier isEqualToString:#"Show Image"]) {
if ([segue.destinationViewController respondsToSelector:#selector(setImageUrl:)]) {
NSURL *url = [[self.photos objectAtIndex:indexPath.row] valueForKey:#"url"];
[segue.destinationViewController performSelector:#selector(setImageUrl:) withObject:url];
[segue.destinationViewController setTitle:[self titleForRow:indexPath.row]];
}
}
}
}
}
whats wrong with the URL? how can i fix it? thank you
i have find the solution:
when i load the url for the model, i need to initialize the url using fileURLWithPath method:
NSURL *url = [NSURL fileURLWithPath:[[self.photos objectAtIndex:indexPath.row] valueForKey:#"url"]];
Now all works fine, thank you so much for yours help

Answer 1

[NSData initWithContentsOfURL:] is expecting an NSURL as the argument passed in. It looks like you might be passing in a string, rather than an NSURL. Is this the case?
EDIT: Just humour me - try replacing
NSData *imageData = [[NSData alloc] initWithContentsOfURL:self.imageUrl];
with
NSData *imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:self.imageUrl]];
What happens?
Though it doesn't look like you're returning successfully from initWithContentsOfURL:, but the snippet below may be of use to others:
NSError *error;
NSData *data = [[NSData alloc] initWithContentsOfURL:TestURL options:0 error:&error];
if(data) {
NSLog(#"Success");
}
else {
NSLog(#"Failed: %#", Error);
}

Answer 2

solution: when i load the url for the model, i need to initialize the url using fileURLWithPath method:
NSURL *url = [NSURL fileURLWithPath:[[self.photos objectAtIndex:indexPath.row] valueForKey:#"url"]];
Now all works fine, thank you so much for yours help