Threading - Core Data - page 87

Baseline/PPRecipes/PPRImportOperation.m
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self
selector: @selector (contextDidSave:)
name:NSManagedObjectContextDidSaveNotification
object:localMOC];
Unlike its PPRExportOperation counterpart, the PPRImportOperation makes changes
to the NSManagedObjectContext ; we'll need to observe the changes and consume
them in the primary NSManagedObjectContext .
Baseline/PPRecipes/PPRImportOperation.m
NSError *error = nil;
id recipesJSON = nil;
recipesJSON = [NSJSONSerialization JSONObjectWithData:[self incomingData]
options:0
error:&error];
if (!recipesJSON) {
[self completionBlock](NO, error);
return ;
}
NSManagedObject *recipeMO = nil;
if ([recipesJSON isKindOfClass:[NSDictionary class]]) {
recipeMO = [NSEntityDescription insertNewObjectForEntityForName:@ "Recipe"
inManagedObjectContext:localMOC];
[self populateManagedObject:recipeMO fromDictionary:recipesJSON];
return ;
} else {
ZAssert([recipesJSON isKindOfClass:[NSArray class]],
@ "Unknown structure root: %@" , [recipesJSON class]);
for (id recipeDict in recipesJSON) {
ZAssert([recipeDict isKindOfClass:[NSDictionary class]],
@ "Unknown recipe structure: %@" , [recipeDict class]);
recipeMO = [NSEntityDescription insertNewObjectForEntityForName:@ "Recipe"
inManagedObjectContext:localMOC];
[self populateManagedObject:recipeMO fromDictionary:recipeDict];
}
ZAssert([localMOC save:&error], @ "Error saving import context: %@\n%@" ,
[error localizedDescription], [error userInfo]);
}
}
The last portion of the -main is where the real work gets done. We start by
using the NSJSONSerializer to convert the NSData into a JSON structure. If that
conversion fails, we call the completion block and finish the operation.