Overview

Processing data is a potential bottleneck for any application that manipulates it.

Older iPhone and iPod touch models get the worst of this with their slower processors and smaller amounts of ram. It's important to pull data processing off of the main UI thread. Nimbus operations provide a consistent means of processing data in a defered way using the NIOperation class of objects.

Suggestions for Picking a Processing Method

Use Blocks and NIOperationDelegate for One-Off Implementations

Blocks are useful when writing inline code quickly, but after a certain point of complexity it may be cleaner to implement the delegate. If your block spans more than 10 lines of code or so, it might be worth considering moving the logic into the delegate method.

Subclass Common Functionality

If you find yourself repeating the same functionality across a variety of controllers then you should consider building a subclass. A good example is NINetworkJSONRequest, which subclasses NINetworkRequestOperation and turns the response data into Objective-C objects. NINetworkRequestOperation can be reused throughout an application as a result.

Examples

Fetching the Name of a Node in the Facebook Graph

  // The graph API path for the Nimbus Facebook group.
  NSString* urlPath = @"https://graph.facebook.com/186162441444201";

  // Create a JSONKit request that will turn the response data into Objective-C objects.
  // Define the request with __block so that it doesn't cause a retain cycle when we access
  // the request object from within the block.
  __block NINetworkJSONRequest* request = [[[NINetworkJSONRequest alloc] initWithURL:
                                            [NSURL URLWithString:urlPath]] autorelease];

  // Called on the operation's thread.
  // We can do computationally expensive operations here without blocking the UI in any way.
  // Note: You must be careful not to access any non-thread-safe objects from within this block.
  request.willFinishBlock = ^(NIOperation* operation) {

    NSString* graphName = nil;

    // By this point the JSON will have been turned into an object.
    graphName = [request.processedObject objectForKey:@"name"];

    // The block expects us to return an id type.
    return (id)graphName;
  };

  // Avoid a retain cycle of self.
  __block UIViewController* vc = self;

  // Called on the main UI thread. This method should be light-weight.
  request.didFinishBlock = ^(NIOperation* operation) {
    NSString* graphName = request.processedObject;
    // Do what we will with the graph name now.
    vc.title = graphName;
  };

  [operationQueue addOperation:request];

Modules
	Network Operations