- (void)main
{
IDBAssert0(self.bestCapture.webpCandidate);
self.finished = NO;
self.executing = YES;
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
UIImage *possiblycorrupted = [UIImage imageWithWebPData:self.bestCapture.webpCandidate];
NSTimeInterval webpInterval = [NSDate timeIntervalSinceReferenceDate]-now;
NSDLog(#"it tooke %.2f sec to unpack webp", webpInterval);
self.microblinkCandidate = possiblycorrupted; // data superclass nsoperation processes
[super main];
}
first thing main in the base class does naturally is setting finished to no and executing to yes:
- (void)main
{
self.finished = NO;
self.executing = YES;
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
start = now;
CGSize size = [self.microblinkCandidate size];
IDBAssert0(size.width && size.height);
IDBAssert0(self.microblink);
// this starts async processing
[self.microblink processImage:self.microblinkCandidate
scanningRegion:CGRectMake(0.0, 0.0, 1.0, 1.0)
delegate:self];
while (![self isCancelled])
{
sleep(1);
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
if(now - start > 5) {
// #5677 microblink watchdog to detect hangs
[self cancel];
break;
}
}
[self done];
}
cause it's not an abstract and will be used on its own as well.
the loop is for debug/watchdog purposes only
in the normal operation it's not tripped an operation is done
if this callback:
- (void)scanningViewController: (UIViewController<PPScanningViewController>*)scanningViewController
didOutputResults:(NSArray*)results
{
if([results count]>0) {
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
NSDLog(#"found barcode in %.1fs", now - start);
self.microblinkSuccessHandler();
}else{
IDBAssert0(self.microblinkFailureHandler);
self.microblinkFailureHandler();
}
[self done];
}
is invoked when "processImage:" will have finished (in a timely fashion).
the very base class is
#implementation IDBAsynchronousOperation
#synthesize executing = _executing;
#synthesize finished = _finished;
-(BOOL)isFinished
{
return _finished;
}
- (void)setFinished:(BOOL)finished
{
[self willChangeValueForKey:#"isFinished"];
_finished = finished;
[self didChangeValueForKey:#"isFinished"];
}
-(BOOL)isExecuting
{
return _executing;
}
- (void)setExecuting:(BOOL)executing
{
[self willChangeValueForKey:#"isExecuting"];
_executing = executing;
[self didChangeValueForKey:#"isExecuting"];
}
- (instancetype)init
{
self = [super init];
if (self) {
// self.completionBlock = ^{
// NSDLog(#"image barcode search has finished");
// };
IDBAssert0(sizeof(_executing)<2);
}
return self;
}
-(BOOL)isAsynchronous
{
return YES;
}
#end
You certainly can (and we often do) subclass your own concrete NSOperation subclass.
To make the base class subclassable, you want to make sure that you only perform self.executing = true once. Right now, the main in both the base class and the subclass do it, and you'll therefore be doing it twice. The typical solution is to pull it out of both of those main implementations and do it in start of the base class. Apple suggests that you do this stuff in start, anyway.
Thus having removed the self.finished and self.executing stuff from both main implementations, you can then implement start:
- (void)start {
if ([self isCancelled]) {
self.finished = YES;
return;
}
self.executing = YES;
[self main];
}
Note, you don't have to call self.finished = false when the operation is starting because that will send an unnecessary KVO.
An unrelated observation:
If you keep the while loop in the base class, I'd suggest exiting the loop if either [self isCancelled] or if the processImage delegate completion methods was called (perhaps you can update some state property to designate when that delegate method was called). Right now, if the processImage finishes before the timeout, it will keep the operation running for the full 5 seconds.
Personally, depending upon how processImage was designed, I probably be inclined excise the while loop entirely. You generally want to avoid any polling like this at all. I might, for example, put the [self done] in the appropriate delegate method and then set up a timer or dispatch_after for the timeout.
- (void)main {
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
start = now;
CGSize size = [self.microblinkCandidate size];
IDBAssert0(size.width && size.height);
IDBAssert0(self.microblink);
// this starts async processing
[self.microblink processImage:self.microblinkCandidate
scanningRegion:CGRectMake(0.0, 0.0, 1.0, 1.0)
delegate:self];
// cancel upon timeout
typeof(self) __weak weakSelf = self;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
typeof(self) __strong strongSelf = weakSelf;
if ([strongSelf isExecuting]) {
[strongSelf cancel];
[strongSelf done]; // if canceling calls the delegate method that calls `done`, then you don't need this here
}
});
}
I will explain scenario.
I have a NSOperation subclass. In this class , I am reading data from multiple bluetooth devices.
I am creating an object of NSOperation class in ViewController A and get data using delegate methods in NSoperation subclass.
Now, I want to read data from Viewcontroller B without creating an object of NSoperation.
Please check my NSOperation Subclass
NOPerationSubclass.h
`
#protocol NOPerationSubclassDelegate`;
#interface NOPerationSubclass : NSOperation{
BOOL executing;
BOOL finished;
}
#property id<NOPerationSubclassDelegate> delegate;
- (id)initWithConnectDevice:(ConnectDevice *)cDevice toPeripheral:(CBPeripheral *)peripheral;
#end
#protocol NOPerationSubclassDelegate
-(void)updateUIFromOperation:(NOPerationSubclass *)operation;
#end
NOPerationSubclass.m
- (id)initWithConnectDevice:(ConnectDevice *)cDevice toPeripheral:(CBPeripheral *)peripheral{
if (self = [super init]) {
executing = NO;
finished = NO;
self.connectDevice = cDevice;
[self.connectDevice setDelegate:self];
self.connectedPeripheral = peripheral;
dataDic = [[NSMutableDictionary alloc] init];
}
return self;
}
-(BOOL)isConcurrent{
return YES;
}
- (BOOL)isExecuting {
return executing;
}
- (BOOL)isFinished {
return finished;
}
-(void) terminateOperation {
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
finished = YES;
executing = NO;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
}
- (void)start {
#autoreleasepool {
if (self.isCancelled){
[self willChangeValueForKey:#"isFinished"];
finished = YES;
[self didChangeValueForKey:#"isFinished"];
return;
}
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(timerFired:) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] run];
}
-(void)timerFired:(id)sender{
if (self.isCancelled){
[self willChangeValueForKey:#"isFinished"];
finished = YES;
[self didChangeValueForKey:#"isFinished"];
return;
}
[connectDevice calldiscoverServicesForPeripheral:connectedPeripheral];
}
-(void)getDataFromPeripheral:(CBPeripheral *)peripheral Data:(NSString *)data{
[dataDic setValue:[peripheral.identifier UUIDString] forKey:#"identifier"];
[dataDic setValue:data forKey:#"data"];
[[[AppDelegate app] devicesDataArray] addObject:dataDic];
[(NSObject *)self.delegate performSelectorOnMainThread:#selector(updateUIFromOperation:) withObject:dataDic waitUntilDone:NO];
NSLog(#"PERIPHERAL DATA::+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++%#",peripheral.name);
}
And, I am calling this NSOpeartion class from ViewController A like this
NOPerationSubclass *queue = [[NOPerationSubclass alloc] initWithConnectDevice:connectDevices toPeripheral:peripheral];
queue.delegate = self;
[[[AppDelegate app] mainOperationQueue] addOperation:queue];
You can use a shared instance class, this is what I always do:
Database.h
#import <Foundation/Foundation.h>
#interface Database : NSObject
#property (nonatomic, readonly) NSArray* myTable;
+(Database*) sharedInstance;
#end
Database.m
#import "Database.h"
#implementation Database
Database* _db = nil;
+(Database*) sharedInstance {
if (!_db)
_db = [[Database alloc] init];
return _db;
}
-(id) init {
self = [super init];
// Do loading here
return self;
}
#end
Then whenever you want to access the data:
[Database sharedInstance].myTable;
I am trying to make use of CLLocationManager in an NSOperation. As part of this I require the ability to startUpdatingLocation then wait until a CLLocation is received before completing the operation.
At present I have done the following, however the delegate method never seems to be called. Please can someone advise what the issue is?
- (void)main
{
#autoreleasepool {
if (self.isCancelled)
return;
// Record the fact we have not found the location yet
shouldKeepLooking = YES;
// Setup the location manager
NSLog(#"Setting up location manager.");
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
while (shouldKeepLooking) {
if (self.isCancelled)
return;
// Do some other logic...
}
}
}
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
// None of this ever seems to be called (despite updating the location)
latestLocation = [locations lastObject];
[manager stopUpdatingLocation];
shouldKeepLooking = NO;
}
Going back to the runloop discussion, this is how I generally solve that in my base NSOperation implementation:
// create connection and keep the current runloop running until
// the operation has finished. this allows this instance of the operation
// to act as the connections delegate
_connection = [[NSURLConnection alloc] initWithRequest:[self request]
delegate:self];
while(!self.isFinished) {
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]];
}
I key off of isFinished, which I keep updated through setters for isCancelled and isFinished. Here's the isCancelled setter as an example:
- (void)setIsCancelled:(BOOL)isCancelled {
_isCancelled = isCancelled;
if (_isCancelled == YES) {
self.isFinished = YES;
}
}
That said, I second some of the questions about why this is necessary. If you don't need to kick something off until a location is found, why not just fire up your location manager on the main thread, wait for the appropriate delegate callback and then kick off the background operation?
Update: updated solution
While the original answer generally stands, I've fully implement a solution and it does require a slight change to how you manage the run loop. That said, all code is available on GitHub - https://github.com/nathanhjones/CLBackgroundOperation. Here is a detailed explanation of the approach.
Tl;dr
Change
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]];
to
[[NSRunLoop currentRunLoop] runMode:NSRunLoopCommonModes
beforeDate:[NSDate distantFuture]];
Details
Within your operations interface define the following three properties. We'll be indicating that these operations are concurrent thus we'll manage their state manually. In the solution on GitHub these are part of NJBaseOperation.
#property(nonatomic,assign,readonly) BOOL isExecuting;
#property(nonatomic,assign,readonly) BOOL isFinished;
#property(nonatomic,assign,readonly) BOOL isCancelled;
Within your operations implementation you'll want to make those readwrite like so:
#interface NJBaseOperation ()
#property(nonatomic,assign,readwrite) BOOL isExecuting;
#property(nonatomic,assign,readwrite) BOOL isFinished;
#property(nonatomic,assign,readwrite) BOOL isCancelled;
#end
Next, you'll want to synthesize the three properties you defined above so that you can override the setters and use them to manage your operations state. Here's what I generally use, but sometimes there are some additional statements added to the setIsFinished: method depending on my needs.
- (void)setIsExecuting:(BOOL)isExecuting {
_isExecuting = isExecuting;
if (_isExecuting == YES) {
self.isFinished = NO;
}
}
- (void)setIsFinished:(BOOL)isFinished {
_isFinished = isFinished;
if (_isFinished == YES) {
self.isExecuting = NO;
}
}
- (void)setIsCancelled:(BOOL)isCancelled {
_isCancelled = isCancelled;
if (_isCancelled == YES) {
self.isFinished = YES;
}
}
Lastly, just so that we don't have to manually send the KVO notifications we'll implement the following method. This works because our properties are named isExecuting, isFinished and isCancelled.
+ (BOOL) automaticallyNotifiesObserversForKey:(NSString *)key {
return YES;
}
Now that the the operations foundation is taken care of it's time to knockout the location stuff. You'll want to override main and within it fire up your location manager and instruct the current run loop to keep running until you tell it otherwise. This ensures that your thread is around to receive the location delegate callbacks. Here's my implementation:
- (void)main {
if (_locationManager == nil) {
_locationManager = [[CLLocationManager alloc] init];
_locationManager.delegate = self;
_locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[_locationManager startUpdatingLocation];
}
while(!self.isFinished) {
[[NSRunLoop currentRunLoop] runMode:NSRunLoopCommonModes
beforeDate:[NSDate distantFuture]];
}
}
You should receive a delegate callback at which point you can do some work based on location and then finish the operation. Here's my implementation that counts to 10,000 and then cleans up.
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
NSLog(#"** Did Update Location: %#", [locations lastObject]);
[_locationManager stopUpdatingLocation];
// do something here that takes some length of time to complete
for (int i=0; i<10000; i++) {
if ((i % 10) == 0) {
NSLog(#"Loop %i", i);
}
}
self.isFinished = YES;
}
The source on GitHub includes a dealloc implementation, which simply logs that it's being called and also observes changes to the operationCount of my NSOperationQueue and logs the count - to indicating when it drops back to 0. Hope that helps. Let me know if you've got questions.
I think you have two options.
Create a separate thread, with its own run loop, for location services:
#import "LocationOperation.h"
#import <CoreLocation/CoreLocation.h>
#interface LocationOperation () <CLLocationManagerDelegate>
#property (nonatomic, readwrite, getter = isFinished) BOOL finished;
#property (nonatomic, readwrite, getter = isExecuting) BOOL executing;
#property (nonatomic, strong) CLLocationManager *locationManager;
#end
#implementation LocationOperation
#synthesize finished = _finished;
#synthesize executing = _executing;
- (id)init
{
self = [super init];
if (self) {
_finished = NO;
_executing = NO;
}
return self;
}
- (void)start
{
if ([self isCancelled]) {
self.finished = YES;
return;
}
self.executing = YES;
[self performSelector:#selector(main) onThread:[[self class] locationManagerThread] withObject:nil waitUntilDone:NO modes:[[NSSet setWithObject:NSRunLoopCommonModes] allObjects]];
}
- (void)main
{
[self startStandardUpdates];
}
- (void)dealloc
{
NSLog(#"%s", __FUNCTION__);
}
#pragma mark - NSOperation methods
- (BOOL)isConcurrent
{
return YES;
}
- (void)setExecuting:(BOOL)executing
{
if (executing != _executing) {
[self willChangeValueForKey:#"isExecuting"];
_executing = executing;
[self didChangeValueForKey:#"isExecuting"];
}
}
- (void)setFinished:(BOOL)finished
{
if (finished != _finished) {
[self willChangeValueForKey:#"isFinished"];
_finished = finished;
[self didChangeValueForKey:#"isFinished"];
}
}
- (void)completeOperation
{
self.executing = NO;
self.finished = YES;
}
- (void)cancel
{
[self stopStandardUpdates];
[super cancel];
[self completeOperation];
}
#pragma mark - Location Manager Thread
+ (void)locationManagerThreadEntryPoint:(id __unused)object
{
#autoreleasepool {
[[NSThread currentThread] setName:#"location manager"];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
[runLoop run];
}
}
+ (NSThread *)locationManagerThread
{
static NSThread *_locationManagerThread = nil;
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_locationManagerThread = [[NSThread alloc] initWithTarget:self selector:#selector(locationManagerThreadEntryPoint:) object:nil];
[_locationManagerThread start];
});
return _locationManagerThread;
}
#pragma mark - Location Services
- (void)startStandardUpdates
{
if (nil == self.locationManager)
self.locationManager = [[CLLocationManager alloc] init];
self.locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
self.locationManager.distanceFilter = 500;
[self.locationManager startUpdatingLocation];
}
- (void)stopStandardUpdates
{
[self.locationManager stopUpdatingLocation];
self.locationManager = nil;
}
#pragma mark - CLLocationManagerDelegate
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
CLLocation* location = [locations lastObject];
// do whatever you want with the location
// now, turn off location services
if (location.horizontalAccuracy < 50) {
[self stopStandardUpdates];
[self completeOperation];
}
}
#end
Alternatively, even though you're using an operation, you could just run location services on the main thread:
#import "LocationOperation.h"
#import <CoreLocation/CoreLocation.h>
#interface LocationOperation () <CLLocationManagerDelegate>
#property (nonatomic, readwrite, getter = isFinished) BOOL finished;
#property (nonatomic, readwrite, getter = isExecuting) BOOL executing;
#property (nonatomic, strong) CLLocationManager *locationManager;
#end
#implementation LocationOperation
#synthesize finished = _finished;
#synthesize executing = _executing;
- (id)init
{
self = [super init];
if (self) {
_finished = NO;
_executing = NO;
}
return self;
}
- (void)start
{
if ([self isCancelled]) {
self.finished = YES;
return;
}
self.executing = YES;
[self startStandardUpdates];
}
#pragma mark - NSOperation methods
- (BOOL)isConcurrent
{
return YES;
}
- (void)setExecuting:(BOOL)executing
{
if (executing != _executing) {
[self willChangeValueForKey:#"isExecuting"];
_executing = executing;
[self didChangeValueForKey:#"isExecuting"];
}
}
- (void)setFinished:(BOOL)finished
{
if (finished != _finished) {
[self willChangeValueForKey:#"isFinished"];
_finished = finished;
[self didChangeValueForKey:#"isFinished"];
}
}
- (void)completeOperation
{
self.executing = NO;
self.finished = YES;
}
- (void)cancel
{
[self stopStandardUpdates];
[super cancel];
[self completeOperation];
}
#pragma mark - Location Services
- (void)startStandardUpdates
{
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
if (nil == self.locationManager)
self.locationManager = [[CLLocationManager alloc] init];
self.locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
self.locationManager.distanceFilter = 500;
[self.locationManager startUpdatingLocation];
}];
}
- (void)stopStandardUpdates
{
[self.locationManager stopUpdatingLocation];
self.locationManager = nil;
}
#pragma mark - CLLocationManagerDelegate
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
CLLocation* location = [locations lastObject];
// do whatever you want with the location
// now, turn off location services
if (location.horizontalAccuracy < 50) {
[self stopStandardUpdates];
[self completeOperation];
}
}
#end
I think I'd be inclined to do the second approach (just making sure that I don't do anything too intensive in didUpdateLocations, or if I did, make sure to do it asynchronously), but both of these approaches appear to work.
Another approach is to keep the run loop alive until the operation is finished:
while (![self isFinished]) {
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]];
}
But this doesn't appear to work in conjunction with CLLocationManager, as runUntilDate doesn't immediately return (it's almost as if CLLocationManager is attaching its own source to the runloop, which prevents it from exiting). I guess you could change the runUntilDate to something a little closer than distantFuture (e.g. [NSDate dateWithTimeIntervalSinceNow:1.0]). Still, I think it's just as easy to run this operation start location services on the main queue, like the second solution above.
Having said that, I'm not sure why you would want to use location manager in an operation at all. It's already asynchronous, so I would just start the location manager from the main queue and call it a day.
UIWebView with UIWebViewDelegate method callbacks in an NSOperation
A server I wanted to grab a URL from a server that changes values based upon JavaScript execution from various browsers. So I slapped a dummy UIWebView into an NSOperation and use that to grab out the value I wanted in the UIWebViewDelegate method.
#interface WBSWebViewOperation () <UIWebViewDelegate>
#property (assign, nonatomic) BOOL stopRunLoop;
#property (assign, nonatomic, getter = isExecuting) BOOL executing;
#property (assign, nonatomic, getter = isFinished) BOOL finished;
#property (copy, nonatomic, readwrite) NSURL *videoURL;
#property (strong, nonatomic) UIWebView *webView;
#end
#implementation WBSWebViewOperation
- (id)init
{
self = [super init];
if (self) {
_finished = NO;
_executing = NO;
}
return self;
}
- (id)initWithURL:(NSURL *)episodeURL
{
self = [self init];
if (self != nil) {
_episodeURL = episodeURL;
}
return self;
}
- (void)start
{
if (![self isCancelled]) {
self.executing = YES;
[self performSelector:#selector(main) onThread:[NSThread mainThread] withObject:nil waitUntilDone:NO modes:[[NSSet setWithObject:NSRunLoopCommonModes] allObjects]];
} else {
self.finished = YES;
}
}
- (void)main
{
if (self.episodeURL != nil) {
NSURLRequest *request = [NSURLRequest requestWithURL:self.episodeURL];
UIWebView *webView = [[UIWebView alloc] init];
webView.delegate = self;
[webView loadRequest:request];
self.webView = webView;
}
}
#pragma mark - NSOperation methods
- (BOOL)isConcurrent
{
return YES;
}
- (void)setExecuting:(BOOL)executing
{
[self willChangeValueForKey:#"isExecuting"];
_executing = executing;
[self didChangeValueForKey:#"isExecuting"];
}
- (void)setFinished:(BOOL)finished
{
[self willChangeValueForKey:#"isFinished"];
_finished = finished;
[self didChangeValueForKey:#"isFinished"];
}
- (void)completeOperation
{
self.executing = NO;
self.finished = YES;
}
- (void)cancel
{
[self.webView stopLoading];
[super cancel];
[self completeOperation];
}
#pragma mark - UIWebViewDelegate methods
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
NSString *episodeVideoURLString = [webView stringByEvaluatingJavaScriptFromString:#"document.getElementById('playerelement').getAttribute('data-media')"];
NSURL *episodeVideoURL = [NSURL URLWithString:episodeVideoURLString];
self.videoURL = episodeVideoURL;
if ([self.delegate respondsToSelector:#selector(webViewOperationDidFinish:)]) {
[self.delegate webViewOperationDidFinish:self];
}
[self completeOperation];
}
#end
Its going to call the delegate method in the same operation queue as main is running in. And NSOperation queues are serial by default. Your while loop is just spinning forever (because the operation is never cancelled) and the call to your delegate method is sitting in the queue behind it never able to run.
Get rid of the while loop entirely and let the operation finish. Then when the delegate method is called, if it's cancelled discard the result by returning.
Typically once the main method of the an NSOperation is completed, the op is marked completed and it is removed from the queue. However, my op makes networking calls, and I want to handle retries. How do I keep an NSOperation in an NSOperationQueue until I explicitly say it's ok to remove it?
I can't find the original source for the work I did on my current project.
I have subclassed NSOperation and do this...
Add private properties in the .m...
#property (nonatomic) BOOL executing;
#property (nonatomic) BOOL finished;
#property (nonatomic) BOOL completed;
Init the operation...
- (id)init
{
self = [super init];
if (self) {
_executing = NO;
_finished = NO;
_completed = NO;
}
return self;
}
Add the functions to return the properties...
- (BOOL)isExecuting { return self.executing; }
- (BOOL)isFinished { return self.finished; }
- (BOOL)isCompleted { return self.completed; }
- (BOOL)isConcurrent { return YES; }
In the "start" function (this is the bit that the operationQueue calls...
- (void)start
{
if ([self isCancelled]) {
[self willChangeValueForKey:#"isFinished"];
self.finished = YES;
[self didChangeValueForKey:#"isFinished"];
return;
}
// If the operation is not canceled, begin executing the task.
[self willChangeValueForKey:#"isExecuting"];
self.executing = YES;
[self didChangeValueForKey:#"isExecuting"];
[NSThread detachNewThreadSelector:#selector(main) toTarget:self withObject:nil];
}
Then in the main put your working code...
- (void)main
{
#try {
//this is where your loop would go with your counter and stuff
//when you want the operationQueue to be notified that the work
//is done just call...
[self completeOperation];
}
#catch (NSException *exception) {
NSLog(#"Exception! %#", exception);
[self completeOperation];
}
}
Write the code for completeOperation...
- (void)completeOperation {
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
self.executing = NO;
self.finished = YES;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
}
That's it.
As long as you have these then the operation will work.
You can add as many other functions and properties as you wish.
In fact, I have actually subclassed this class as I have a function that does all the work for different types of object (it's an upload thing). I have defined a function...
- (void)uploadData
{
//subclass this method.
}
Then all I have in the subclasses is a custom "uploadData" method.
I find this really useful as it gives you fine grain control on when to finish the operation etc...
I have a problem. In my program I need to cancel operations (subclass NSOperation) in queue after clicking on button. But when I calling [queue cancelAllOperations] nothing happens. The queue continue executing. All operations must be concurrent. What am I doing wrong?
#interface SearchOperation : NSOperation
{
TrueSearcherViewController *viewController;
SearchYouTube *you_search;
SearchGoogle *goo_search;
BOOL semafore;
}
- (id)initYoutubeTaskWithData:(SearchYouTube *) sy;
- (id)initGoogleTaskWithData:(SearchGoogle *) sg;
- (void) beginYoutubeSearch:(SearchYouTube *) sy;
- (void) beginGoogleSearch:(SearchGoogle *) sg;
#end
#import "SearchOperation.h"
#implementation SearchOperation
- (void) start
{
if (semafore == YES)
{
[self beginYoutubeSearch:you_search];
}
else
{
[self beginGoogleSearch:goo_search];
}
}
- (id)initYoutubeTaskWithData:(SearchYouTube *) sy
{
if (self = [super init])
{
you_search = sy;
semafore = YES;
}
return self;
}
- (id)initGoogleTaskWithData:(SearchGoogle *) sg
{
if (self = [super init])
{
goo_search = sg;
semafore = NO;
}
return self;
}
- (void) beginYoutubeSearch:(SearchYouTube *) sy
{
[sy runSearch];
}
- (void) beginGoogleSearch:(SearchGoogle *) sg
{
[sg runSearch];
}
- (void) dealloc
{
[super dealloc];
}
#end
You need to check in your code if your operation is cancelled to interrupt it with :
if(self.isCancelled){
return;
}