Converting NSData to NSUrl nil string parameter - ios

Question

I am trying to convert NSdata to NSUrl, and I found this method on the internet:
NSString *urlString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
NSURL *url = [[NSURL alloc] initWithString:urlString];
[session sendResourceAtURL:url withName:#"Resource" toPeer:peerID withCompletionHandler:nil];
Seems all right to me, but the app crashes at the second line and gives the error:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSURL initWithString:relativeToURL:]: nil string parameter'
Can't get why...

Answer 1

myData is not UTF-8 encoded.
From the NSString docs:
Returns nil if the initialization fails for some reason (for example
if data does not represent valid data for encoding).
You should always check for this type of condition...
NSString *urlString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
NSURL *url;
if (urlString) {
url = [[NSURL alloc] initWithString:urlString];
} else {
// handle failure
}
Additionally, make sure you're using UTF8 encoding when you create the myData object, or switch from NSUTF8StringEncoding to the correct encoding type.

Answer 2

If dict from [NSKeyedArchiver archivedDataWithRootObject:dict] is NSDictionary class then you must extract the urlString from that dictionary.
NSError* error;
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSString *urlString = [dictionary valueForKey:#"url"];

Answer 3

change the encoding, say to NSUTF16StringEncoding

Answer 4

your String returns null try these method
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:#".png"];
[fileManager createFileAtPath:fullPath contents:myData attributes:nil];
if ([[NSFileManager defaultManager] fileExistsAtPath:fullPath])
{
NSURL *imageUrl = [NSURL fileURLWithPath:fullPath isDirectory:NO];
}