Why is my NSOperation subclass never finishing? - cocoa-touch

Question

I have an NSOperation subclass that I want to run concurrently.
My understanding is that for concurrent operations to work:
I need to define isConcurrent to return YES.
I need to define the start method
I need to send KVOs notification for isExecuting and isFinished when it's done.
Using #synthesize will automatically send the appropriate KVO notifications when the values for isExecuting and isFinished are changed.
Despite this, I have verified that my queue never moves on to the next item.
Here's the meat of my code:
#interface MyOperation()
#property (readwrite) BOOL isExecuting;
#property (readwrite) BOOL isFinished;
#end
#implementation MyOperation
- (void)start
{
#autoreleasepool {
self.isExecuting = YES;
self.HTTPOperation = [[AFHTTPRequestOperation alloc] initWithRequest: URLRequest];
_HTTPOperation.completionBlock = [^{
[self completed];
self.isExecuting = NO;
self.isFinished = YES;
} copy];
[_HTTPOperation start];
}
}
- (BOOL)isConcurrent
{
return YES;
}
- (void)completed
{
}
#end
What am I missing?
(This is on an iPhone, but I can't imagine that matters.)

Answer 1

It looks like whatever KVO notifications #synthesize sends aren't enough for NSOperationQueue to move on.
Sending the notifications manually fixes the problem:
- (void)start
{
#autoreleasepool {
[self willChangeValueForKey:#"isExecuting"];
self.isExecuting = YES;
[self didChangeValueForKey:#"isExecuting"];
NSURLRequest *URLRequest = [self buildRequest];
if (!URLRequest) {
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
_isExecuting = NO;
_isFinished = YES;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
return;
}
self.HTTPOperation = [[AFHTTPRequestOperation alloc] initWithRequest: URLRequest];
_HTTPOperation.completionBlock = [^{
[self completed];
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
_isExecuting = NO;
_isFinished = YES;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
} copy];
[_HTTPOperation start];
}
}
See also:
Why does NSOperation disable automatic key-value observing?

Answer 2

What's your "queue" look like? Are you using an NSOperationQueue?
Anyway, I'll try to answer your question with what I understood :P
I would create a delegate for my NSOperation and have KVO take care of calling this.
Say for example your NSOperation class looks like this
#interface MyOperation : NSOperation
#property (assign) id<MyOperationDelegate> delegate;
Your implementation
#synthesize delegate;
#synthesize error;
-(id)init{
self = [super init];
if(self){
[self addObserver:self forKeyPath:#"isFinished"
options:NSKeyValueObservingOptionNew
context:NULL];
}
return self;
}
-(void)dealloc{
[self removeObserver:self forKeyPath:#"isFinished"];
[super dealloc];
}
-(void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
if([keyPath isEqualToString:#"isFinished"] == YES){
if([self isCancelled] == NO){
if(delegate != nil && [delegate respondsToSelector:#selector(operationComplete:)]){
[delegate taskComplete:self];
}
}else{
if(delegate != nil && [delegate respondsToSelector:#selector(operationCancelled)]){
[delegate taskCancelled];
}
}
}
}
-(void)main{
[NSException exceptionWithName:kTaskException
reason:#"Only to be used with subclass"
userInfo:nil];
}
And finally your protocol
#class MyOperation;
#protocol MyOperationDelegate <NSObject>
#optional
-(void)operationComplete:(MyOperation*)operation;
-(void)operationCancelled;