Big Boy Xcode Threading & Caching

My first actual threaded op;

Threading for operations that need to run in the background (see bottom of this section for the answer!)

Here's a typically excellent Ray W tutorials  (some of following shots & text courtesy of Ray W, hope you don't mind)
And an even simpler (yay!) tutorial turbo-charging-your-apps-with-nsoperation/

Notes: 
Consists of Task, Thread & Process per this sketch;


NSOperation and NSOperationQueue add a little extra overhead compared to GCD, but you can add dependency among various operations. You can re-use operations, cancel or suspend them. NSOperation is compatible with Key-Value Observation (KVO).

Programatic VC creation w/o storyboard (interesting?)

Here, we wrap our ListViewController in a UINavigationController, and set it as the

root view controller.
     */
 
    ListViewController *listViewController = [[ListViewController alloc] 

initWithStyle:UITableViewStylePlain];
    UINavigationController *navController = [[UINavigationController alloc] 

initWithRootViewController:listViewController];
 
    self.window.rootViewController = navController;

As a general rule, if you are executing on a secondary thread and 

you must do something to a UIKit object, use performSelectorOnMainThread.

 Also, if you want to do something that is related to the UI in the block, you must 

do it on the main thread:

Here is the process for a NSOperationQueue

1. Instantiate a new NSOperationQueue object
2. Create an instance of your NSOperation
3. Add your operation to the queue
4. Release your operation

OK But simply?!?

Thanks - http://pinkstone.co.uk/how-to-execute-a-method-on-a-background-thread-in-ios/

This uses GCD Grand Central Dispatch, and works well.  Updating the UI is on the main thread

- (void)loadInBackground
{
    NSLog(@"This is for a background thread");   
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self addPics];
        //update UI on the main thread
        dispatch_async(dispatch_get_main_queue(), ^{          
            //Add the screenMarker array to the layer
            [theViewC addScreenMarkers:theMarkers desc:nil];
        });
    });
}




Now for a Little more complexity
let's try and use NSOperationQueue