I'm making an application in which,I have to make my Inappurchase product auto renewable,for this, after reading Apple documents i came to know that after every transaction for autorenewable product ,our app receives a transaction receipt for every purchase and i need to verify that receipt from Apple server after verifying my transaction receipt app has to save that transaction date.
But after purchasing product when i am trying to verifying that transaction receipt from Apple server ,through the Apple Classes -Verification Controller, my app crashing at completion handler ,its showing completion handler NIL.
my _completionHandlers is released when execution reaches in any of these methods what to now??
Please guide me to solve this issue
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
// So we got some receipt data. Now does it all check out?
BOOL isOk = [self doesTransactionInfoMatchReceipt:responseString];
VerifyCompletionHandler completionHandler = _completionHandlers[[NSValue valueWithNonretainedObject:connection]];
NSValue *key = [NSValue valueWithNonretainedObject:connection];
NSLog(#"%#",_completionHandlers);
[_completionHandlers removeObjectForKey:key];
if (isOk)
{
//Validation suceeded. Unlock content here.
NSLog(#"Validation successful");
completionHandler(TRUE);
} else {
NSLog(#"Validation failed");
completionHandler(FALSE);
}
}
I also ran into this problem i fixed this issue this way
main issue is when you are setting value to completion handler in verifyPurchase method it is setting nil value so find this line in verifyPurchase method
_completionHandlers[[NSValue valueWithNonretainedObject:conn]] = completionHandler;
and replace it with
[_completionHandlers setObject:[completionHandler copy] forKey:[NSValue valueWithNonretainedObject:conn]];
changing these two lines will resolve your crash but to be double sure do these steps also
and find the connectionDidReceivedata method and replace it with
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
// So we got some receipt data. Now does it all check out?
BOOL isOk = [self doesTransactionInfoMatchReceipt:responseString];
if (_completionHandlers && [_completionHandlers respondsToSelector:#selector(removeObjectForKey:)])
{
VerifyCompletionHandler completionHandler = _completionHandlers[[NSValue valueWithNonretainedObject:connection]];
[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
if (isOk)
{
//Validation suceeded. Unlock content here.
NSLog(#"Validation successful");
completionHandler(TRUE);
} else {
NSLog(#"Validation failed");
completionHandler(FALSE);
}
}
//[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
}
Related
I am trying to retrieve a Facebook profile picture, however I am having trouble being able to check when the image has been downloaded?
First I create a variable.
#property (strong, nonatomic) NSMutableData *imageData;
Than I start the connection.
-(void)getUserPicture {
//Grab user profile picture
imageData = [[NSMutableData alloc] init]; // the image will be loaded in here
NSString *urlString = [NSString stringWithFormat:#"http://graph.facebook.com/%#/picture?type=large", userId];
NSMutableURLRequest *urlRequest =
[NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlString]];
NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest:urlRequest
delegate:self];
if (!urlConnection) NSLog(#"Failed to download picture");
}
After that I try to check when it is done so I can upload the file to my backend, however my problem is connectionDidFinishLoading calls almost instantly before the image has downloaded.
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
imageData = [NSMutableData data];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[imageData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
userPicture = [UIImage imageWithData:imageData];
NSLog(#"%#",userPicture); //this returns null :(
}
The weird thing is if I call this method twice, the NSLog doesn't return null, it actually returns the photo. So why is connectionDidFinishedLoading calling before the image has downloaded from Facebook?
The problem is almost certainly neither NSURLConnection nor the Facebook API, but rather how you're calling it. But, your question doesn't include enough information for us to diagnose it.
So, first, expand your methods to include more diagnostic information, for example:
// check the response header when we receive the response
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
imageData = [NSMutableData data];
// if `statusCode` is not 200, show us what it was ...
if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
int statusCode = [(NSHTTPURLResponse *)response statusCode];
if (statusCode != 200) {
NSLog(#"Status code was %ld, but should be 200.", (long)statusCode);
NSLog(#"response = %#", response);
}
}
}
// make sure to detect and report any errors
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSLog(#"didFailWithError: %#", error);
}
// when you're done, if we fail to create `UIImage`, then it obviously
// wasn't an image, so let's see what it was.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
userPicture = [UIImage imageWithData:imageData];
// if not an image, then ...
if (!userPicture) {
NSString *responseString = [[NSString alloc] initWithData:imageData encoding:NSUTF8StringEncoding];
if (responseString) {
// if it was a string, show it to us ...
NSLog(#"did not receive image: responseString = %#", responseString);
} else {
// if neither a string nor image data, then what was it ...
NSLog(#"did not receive image: imageData = %#", imageData);
}
}
// By the way, I'd expect to see you do something here to update the UI with the image;
// all of these delegate methods were called asynchronously, so you have
// to do something here that triggers the update of the UI, e.g.
//
// self.imageView.image = userPicture
}
By the way, I typed the above without the benefit of Xcode's syntax checking and the like, so don't be surprised if there are some errors there. But worry less about the actual code and focus on the the three diagnostic pillars this illustrates: 1. Look at the response headers and make sure they're ok, not reporting some non-200 status code; 2. Implement delegate that will report networking errors; and 3. If image conversion failed, then you obviously didn't receive an image, so stop and figure out what you actually received. (Often if the server had trouble fulfilling your request, the response is actually HTML or something like that which tells you why it had problems. If you don't look at it, you're flying blind.)
Second, you can watch the network connection by using Charles (or something like that). Run the app on the simulator and then watch the network connection as the app runs.
Third, if you're still having problems, create a MCVE. Namely, we don't want to see all of your code, but you should instead create the simplest possible example that manifests the problem you describe. Don't ask us to pour through tons of code, but rather make it as absolutely bare-bones as possible.
So I'm not sure why connectionDidFinishLoading is getting called instantly after you set the connection, but I may be able to help you work around the issue.
Try this:
-(UIImage *) getImageFromURL:(NSString *)fileURL {
UIImage * result;
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
result = [UIImage imageWithData:data];
return result;
}
Where fileURL is the a string with the url.
If you want to perform an action after the request is sent try this instead:
-(UIImage *) getImageFromURL:(NSString *)fileURL {
UIImage * result;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
result = [UIImage imageWithData:data];
return result;
dispatch_async(dispatch_get_main_queue(), ^{
//code for operation after download
});
});
}
Let me know how it goes
I am working on iOS application where I am using Twilio SDK to manage client calling through device. To implement this i am using hello monkey demo application which i have successfully imported in Xcode.
After initial setup i am able to establish connection successfully but receiving delegate is no longer working. I have gone through complete twilio documentation but no success. Please suggest any alternative or solution ASAP.
Here is my code of Hello Monkey sample project
- (void)viewDidLoad
{
NSLog(#"CLINT ID----------------------- %#",name);
//check out https://github.com/twilio/mobile-quickstart to get a server up quickly
NSString *urlString = [NSString stringWithFormat:#"https://testdemo786.herokuapp.com/token?client=%#", name];
NSURL *url = [NSURL URLWithString:urlString];
NSError *error = nil;
NSString *token = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
if (token == nil) {
NSLog(#"Error retrieving token: %#", [error localizedDescription]);
} else {
_phone = [[TCDevice alloc] initWithCapabilityToken:token delegate:self];
}
}
- (IBAction)dialButtonPressed:(id)sender
{
NSString *to;
if ([name isEqualToString:#"jenny"]) {
to=#"client:tommy";
}
else
{
to=#"client:jenny";
}
to=#"4nmf5j";
NSLog(#"TO---------------------%#",to);
NSDictionary *params = #{#"To": to};
_connection = [_phone connect:params delegate:nil];
}
- (IBAction)hangupButtonPressed:(id)sender
{
[_connection disconnect];
}
- (void)device:(TCDevice *)device didReceiveIncomingConnection:(TCConnection *)connection
{
NSLog(#"Incoming connection from: %#", [connection parameters][#"From"]);
if (device.state == TCDeviceStateBusy) {
[connection reject];
} else {
[connection accept];
_connection = connection;
}
}
-(void)connection:(TCConnection*)connection didFailWithError: (NSError*)error{
NSLog(#"Connection failed with error : %#", error);
}
-(void)connectionDidStartConnecting:(TCConnection*)connection{
NSLog(#"connection started");
}
-(void)connectionDidDisconnect:(TCConnection*)connection{
NSLog(#"connection disconnected");
}
-(void)connectionDidConnect:(TCConnection*)connection{
NSLog(#"connected");
}
- (void)deviceDidStartListeningForIncomingConnections: (TCDevice*)device
{
NSLog(#"Device: %# deviceDidStartListeningForIncomingConnections", device);
}
- (void)device:(TCDevice *)device didStopListeningForIncomingConnections:(NSError *)error
{
NSLog(#"Device: %# didStopListeningForIncomingConnections: %#", device, error);
}
Twilio evangelist here.
Its a bit hard to tell from the code you included, which does look correct to me.
Here are a couple of things to check:
Did you add the TCDeviceDelegate as a protocol on your interface:
#interface FooViewController() <TCDeviceDelegate>
Are you sure you passing the correct client name to the connect method, and that the TwiML being returned from your TwiML Apps Voice Request URL is including that name properly?
You could check this by looking at the Twilio Monitor to see if Twilio logged any errors when retrieving or parsing your TwiML. You can also check your Twilio call logs to see what Twilio says the outcome of the inbound and outbound call legs were.
Hope that helps.
did you set the delegate to self?
_device = [[TCDevice alloc] initWithCapabilityToken:capabilityToken delegate:self];
Here is the function where it crashes. The exact line of code is the one with: removeObjectForKey. Even when the test function is completely empty it crashes on removeObjectForKey. Note: I'm just passing in an empty function callback. currently, I have ARC off, do i need to turn it on? If possible, i would like to do it with ARC off, because turning it on would mean dealing with alot of compile issues.
the function does say something about non-retained objects, hence could be a memory issue.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
// So we got some receipt data. Now does it all check out?
BOOL isOk = [self doesTransactionInfoMatchReceipt:responseString];
VerifyCompletionHandler completionHandler = _completionHandlers[[NSValue valueWithNonretainedObject:connection]];
[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
if (isOk)
{
//Validation suceeded. Unlock content here.
NSLog(#"Validation successful");
completionHandler(TRUE);
} else {
NSLog(#"Validation failed");
completionHandler(FALSE);
}
}
Here is the verificationController usage:
[[VerificationController sharedInstance] verifyPurchase:transaction completionHandler:^(BOOL success) {
if (success) {
NSLog(#"Hi, its success.");
[self testMethod];
} else {
NSLog(#"payment not authorized.");
}
}];
}
- (void) testMethod {
}
I could use __weak but then I would have to turn on ARC, which i'm trying to avoid. Note: the verificaitionController works when I put it inside other Classes/Objects, but as soon as I put it in the InAppPurchaseManager it blows up anytime it tries to access self. Self points to an instance of InAppPurchaseManager as defined like so (its a phonegap plugin):
#interface InAppPurchaseManager : CDVPlugin <SKPaymentTransactionObserver> {
}
I also ran into this problem i fixed this issue this way
main issue is when you are setting value to completion handler in verifyPurchase method it is setting nil value so find this line in verifyPurchase method
_completionHandlers[[NSValue valueWithNonretainedObject:conn]] = completionHandler;
and replace it with
[_completionHandlers setObject:[completionHandler copy] forKey:[NSValue valueWithNonretainedObject:conn]];
and find the connectionDidReceivedata method and replace it with
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
// So we got some receipt data. Now does it all check out?
BOOL isOk = [self doesTransactionInfoMatchReceipt:responseString];
if (_completionHandlers && [_completionHandlers respondsToSelector:#selector(removeObjectForKey:)])
{
VerifyCompletionHandler completionHandler = _completionHandlers[[NSValue valueWithNonretainedObject:connection]];
[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
if (isOk)
{
//Validation suceeded. Unlock content here.
NSLog(#"Validation successful");
completionHandler(TRUE);
} else {
NSLog(#"Validation failed");
completionHandler(FALSE);
}
}
//[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
}
Hope this may help you and saves alot of time.
Is _completionHandlers nil? You might do something like this -
if (_completionHandlers && [_completionHandlers respondsToSelector:#selector(removeObjectForKey:)]) {
[_completionHandlers removeObjectForKey:[NSValue valueWithNonretainedObject:connection]];
}
Good luck.
Find following string:
[_completionHandlers setObject:completionHandler forKey:[NSValue valueWithNonretainedObject:conn]];
And change to:
[_completionHandlers setObject:[completionHandler copy] forKey:[NSValue valueWithNonretainedObject:conn]];
I don't know if you found the answer yet, but I just realized that _completionHandlers is never allocated (and if you po _completionHandlers after setting a breakpoint you will notice it is nil). Hope this helps!
// in VerificationController.m
- (id)init
{
self = [super init];
if (self != nil)
{
transactionsReceiptStorageDictionary = [NSMutableDictionary dictionary];
_completionHandlers = [NSMutableDictionary dictionary];
}
return self;
}
Short version of the question:
What is wrong with the following Kiwi/iOS mock expectation?
[[mockDelegate should] receive:#selector(connectionDidSucceedWithText:andStatus:) withArguments:[testString1 stringByAppendingString:testString2],theValue(value),nil];
Long version of question:
I am trying to write a test in Kiwi, iOS for a simple class that handles a NSConnection. To test that the class handles the callback from the NSConnection I send it the delegate methods NSConnection normally does. I have a delegate in the class that sends data back to whoever uses my class. To test my class I have to inject a mocked delegate and then check that my desired methods are called. Simple as that :)
My code for the Kiwi test is:
//Some ivars declared elsewhere:
testString1 = #"asd323/4 d14";
testString2 = #"as98 /2y9h3fdd14";
testData1 = [testString1 dataUsingEncoding:NSUTF8StringEncoding];
testData2 = [testString2 dataUsingEncoding:NSUTF8StringEncoding];
mockURLRespons = [NSHTTPURLResponse mock];
int value = 11111;
id mockDelegate = [KWMock mockForProtocol:#protocol(SharepointConnectionDelegate)];
communicator = [[SharepointCommunicator alloc] init];
it (#"should send recieve data back to delegate2", ^{
[communicator setDelegate:mockDelegate];
[mockURLRespons stub:#selector(statusCode) andReturn:theValue(value)];
[(id)communicator connection:niceMockConnector didReceiveResponse:mockURLRespons];
[(id)communicator connection:niceMockConnector didReceiveData:testData1];
[(id)communicator connection:niceMockConnector didReceiveData:testData2];
[(id)communicator connectionDidFinishLoading:niceMockConnector];
[[mockDelegate should] receive:#selector(connectionDidSucceedWithText:andStatus:) withArguments:[testString1 stringByAppendingString:testString2],theValue(value),nil];
});
And in my SharepointCommunicator.m:
-(void)connection:(NSURLConnection *)aConnection didReceiveResponse:(NSURLResponse *)response {
if (connection != aConnection) {
[connection cancel];
connection = aConnection;
}
responseData = [[NSMutableData alloc] init];
statusCode = [(NSHTTPURLResponse*)response statusCode];
}
-(void)connection:(NSURLConnection *)aConnection didReceiveData:(NSData *)data {
if (aConnection != self.connection)
return;
[responseData appendData:data];
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSString *txt = [[NSString alloc] initWithData:responseData encoding: NSASCIIStringEncoding];
NSLog(#"Statuscode: %i", statusCode);
NSLog(#"Data is: %#",txt);
[delegate connectionDidSucceedWithText:txt andStatus:statusCode];
[self.connection cancel];
self.connection = nil;
}
This code works and is correct. Debugging it with checkpoint shows it does as expected. The values of statusCode is 11111. and txt is testString1+textString2. Still it fails on the last row on in the test with the following error:
error: -[kiwiSharepointCommunicatorTest Sharepointcommunicator_AStateTheComponentIsIn_ShouldSendRecieveDataBackToDelegate2] : 'Sharepointcommunicator, a state the component is in, should send recieve data back to delegate2' [FAILED], mock received unexpected message -connectionDidSucceedWithText:"asd323/4 d14as98 /2y9h3fdd14" andStatus:11111
Test Case '-[kiwiSharepointCommunicatorTest Sharepointcommunicator_AStateTheComponentIsIn_ShouldSendRecieveDataBackToDelegate2]' failed (3.684 seconds).
Removing the last row in the test still generate the same error. I guess my understanding of receive:withArguments: is wrong..
You have to call [[mockDelegate should] receive... before the call to connectionDidFinishLoading to prepare the mockDelegate for the message it's about to receive.
We have a large project that needs to sync large files from a server into a 'Library' in the background. I read subclassing NSOperation is the most flexible way of multithreading iOS tasks, and attempted that. So the function receives a list of URLs to download & save, initialises an instance of the same NSOperation class and adds each to an NSOperation queue (which should download only 1 file at a time).
-(void) LibSyncOperation {
// Initialize download list. Download the homepage of some popular websites
downloadArray = [[NSArray alloc] initWithObjects:#"www.google.com",
#"www.stackoverflow.com",
#"www.reddit.com",
#"www.facebook.com", nil];
operationQueue = [[[NSOperationQueue alloc]init]autorelease];
[operationQueue setMaxConcurrentOperationCount:1]; // Only download 1 file at a time
[operationQueue waitUntilAllOperationsAreFinished];
for (int i = 0; i < [downloadArray count]; i++) {
LibSyncOperation *libSyncOperation = [[[LibSyncOperation alloc] initWithURL:[downloadArray objectAtIndex:i]]autorelease];
[operationQueue addOperation:libSyncOperation];
}
}
Now, those class instances all get created fine, and are all added to the NSOperationQueue and begin executing. BUT the issue is when it's time to start downloading, the first file never begins downloading (using an NSURLConnection with delegate methods). I've used the runLoop trick I saw in another thread which should allow the operation to keep running until the download is finished. The NSURLConnection is established, but it never starts appending data to the NSMutableData object!
#synthesize downloadURL, downloadData, downloadPath;
#synthesize downloadDone, executing, finished;
/* Function to initialize the NSOperation with the URL to download */
- (id)initWithURL:(NSString *)downloadString {
if (![super init]) return nil;
// Construct the URL to be downloaded
downloadURL = [[[NSURL alloc]initWithString:downloadString]autorelease];
downloadData = [[[NSMutableData alloc] init] autorelease];
NSLog(#"downloadURL: %#",[downloadURL path]);
// Create the download path
downloadPath = [NSString stringWithFormat:#"%#.txt",downloadString];
return self;
}
-(void)dealloc {
[super dealloc];
}
-(void)main {
// Create ARC pool instance for this thread.
// NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; //--> COMMENTED OUT, MAY BE PART OF ISSUE
if (![self isCancelled]) {
[self willChangeValueForKey:#"isExecuting"];
executing = YES;
NSURLRequest *downloadRequest = [NSURLRequest requestWithURL:downloadURL];
NSLog(#"%s: downloadRequest: %#",__FUNCTION__,downloadURL);
NSURLConnection *downloadConnection = [[NSURLConnection alloc] initWithRequest:downloadRequest delegate:self startImmediately:NO];
// This block SHOULD keep the NSOperation from releasing before the download has been finished
if (downloadConnection) {
NSLog(#"connection established!");
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
} while (!downloadDone);
} else {
NSLog(#"couldn't establish connection for: %#", downloadURL);
// Cleanup Operation so next one (if any) can run
[self terminateOperation];
}
}
else { // Operation has been cancelled, clean up
[self terminateOperation];
}
// Release the ARC pool to clean out this thread
//[pool release]; //--> COMMENTED OUT, MAY BE PART OF ISSUE
}
#pragma mark -
#pragma mark NSURLConnection Delegate methods
// NSURLConnectionDelegate method: handle the initial connection
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse*)response {
NSLog(#"%s: Received response!", __FUNCTION__);
}
// NSURLConnectionDelegate method: handle data being received during connection
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[downloadData appendData:data];
NSLog(#"downloaded %d bytes", [data length]);
}
// NSURLConnectionDelegate method: What to do once request is completed
-(void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSLog(#"%s: Download finished! File: %#", __FUNCTION__, downloadURL);
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docDir = [paths objectAtIndex:0];
NSString *targetPath = [docDir stringByAppendingPathComponent:downloadPath];
BOOL isDir;
// If target folder path doesn't exist, create it
if (![fileManager fileExistsAtPath:[targetPath stringByDeletingLastPathComponent] isDirectory:&isDir]) {
NSError *makeDirError = nil;
[fileManager createDirectoryAtPath:[targetPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:&makeDirError];
if (makeDirError != nil) {
NSLog(#"MAKE DIR ERROR: %#", [makeDirError description]);
[self terminateOperation];
}
}
NSError *saveError = nil;
//NSLog(#"downloadData: %#",downloadData);
[downloadData writeToFile:targetPath options:NSDataWritingAtomic error:&saveError];
if (saveError != nil) {
NSLog(#"Download save failed! Error: %#", [saveError description]);
[self terminateOperation];
}
else {
NSLog(#"file has been saved!: %#", targetPath);
}
downloadDone = true;
}
// NSURLConnectionDelegate method: Handle the connection failing
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSLog(#"%s: File download failed! Error: %#", __FUNCTION__, [error description]);
[self terminateOperation];
}
// Function to clean up the variables and mark Operation as finished
-(void) terminateOperation {
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
finished = YES;
executing = NO;
downloadDone = YES;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
}
#pragma mark -
#pragma mark NSOperation state Delegate methods
// NSOperation state methods
- (BOOL)isConcurrent {
return YES;
}
- (BOOL)isExecuting {
return executing;
}
- (BOOL)isFinished {
return finished;
}
NOTE: If that was too unreadable, I set up a QUICK GITHUB PROJECT HERE you can look through. Please note I'm not expecting anyone to do my work for me, simply looking for an answer to my problem!
I suspect it has something to do with retaining/releasing class variables, but I can't be sure of that since I thought instantiating a class would give each instance its own set of class variables. I've tried everything and I can't find the answer, any help/suggestions would be much appreciated!
UPDATE: As per my answer below, I solved this problem a while ago and updated the GitHub project with the working code. Hopefully if you've come here looking for the same thing it helps!
In the interests of good community practice and helping anyone else who might end up here with the same problem, I did end up solving this issue and have updated the GitHub sample project here that now works correctly, even for multiple concurrent NSOperations!
It's best to look through the GitHub code since I made a large amount of changes, but the key fix I had to make to get it working was:
[downloadConnection scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
This is called after the NSURLConnection is initialized, and just before it is started. It attaches the execution of the connection to the current main run loop so that the NSOperation won't prematurely terminate before the download is finished. I'd love to give credit to wherever first posted this clever fix, but it's been so long I've forgotten where, apologies. Hope this helps someone!