iPhone-SDK:Call a function in the background?

Question

Is it possible to call my function in the background after certain interval programmatically in iPhone SDK development? I want to call one particular function in the backgro

Answer 1

To call the function on the main thread, use an NSTimer.

To call it on another thread, create an NSOperation and set up an NSOperationQueue to call it.

Answer 2

You can have a timer, look into NSTimer for that that will fire off every 10 minutes, in order to make i t happen i n the background you have a few options ill name two. First of note that any UI work should not be done in another thread since UIKit is not thread safe.

• You can subclass NSThread and use it to do you process in the background

• You can use NSObjects performSelectorInBackground method which basically creates a thread and executes the method. Heres a reference http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html#//apple_ref/occ/instm/NSObject/performSelectorInBackground:withObject:

NSThread reference here http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSThread_Class/Reference/Reference.html

NSTimer reference here http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSTimer_Class/Reference/NSTimer.html

Answer 3

Easiest way is to schedule a NSTimer on the main threads run-loop. I suggest that the following code is implemented on your application delegate, and that you call setupTimer from applicationDidFinishLaunching:.

-(void)setupTimer;
{
  NSTimer* timer = [NSTimer timerWithTimeInterval:10 * 60
                                           target:self
                                         selector:@selector(triggerTimer:)
                                         userInfo:nil
                                          repeats:YES];
  [[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
}

-(void)triggerTimer:(NSTimer*)timer;
{
  // Do your stuff
}

If your stuff here takes a long time, and you can not hold up the main thread then either call your stuff using:

[self performSelectorInBackground:@selector(myStuff) withObject:nil];

Or you could run the NSTimer on a background thread by with something like this (I am intentionally leaking the thread object):

-(void)startTimerThread;
{
  NSThread* thread = [[NSThread alloc] initWithTarget:self
                                             selector:@selector(setupTimerThread)
                                           withObject:nil];
  [thread start];
}

-(void)setupTimerThread;
{
  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
  NSTimer* timer = [NSTimer timerWithTimeInterval:10 * 60
                                           target:self
                                         selector:@selector(triggerTimer:)
                                         userInfo:nil
                                          repeats:YES];
  NSRunLoop* runLoop = [NSRunLoop currentRunLoop];
  [runLoop addTimer:timer forModes:NSRunLoopCommonModes];
  [runLoop run];
  [pool release];
}

-(void)triggerTimer:(NSTimer*)timer;
{
  // Do your stuff
}