Threading - Core Data: Data Storage and Management for iOS, OS X, and iCloud - page 80

Figure 15—Linking the Import menu item
When the user taps Mail Recipe, the switch statement calls our -mailRecipe
method.
Baseline/PPRecipes/PPRDetailViewController.m
- ( void )mailRecipe
{
PPRExportOperation *operation = nil;
operation = [[PPRExportOperation alloc] initWithRecipe:[self recipeMO]];
[operation setCompletionBlock:^(NSData *data, NSError *error) {
ZAssert(data || !error, @ "Error: %@\n%@" , [error localizedDescription],
[error userInfo]);
//Mail the data to a friend
}];
[[NSOperationQueue mainQueue] addOperation:operation];
}