Question

I am using a WCF service in my app.When the app is run for the first time on the iPad,I want it to call a WCF service and display the result in a UITableView.Alongwith displaying the data in UITableView,i want to store the data in Core Data so when the user is “offline”(not connected to wifi)the data will be displayed from the Core Data.The AppDelegate.m looks like this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];  
    if (![defaults objectForKey:@"firstRun"])
    {
        self.firstRun = TRUE;
        [defaults setObject:[NSDate date] forKey:@"firstRun"];
    }
    else
    {
       self.firstRun = FALSE;//flag does exist so this ISNT the first run
    }
   [[NSUserDefaults standardUserDefaults] synchronize];
}

The code in UITableView looks like this:

- (void)viewDidLoad
{
    [super viewDidLoad];
    [my_table setDataSource:self];
    [my_table setDelegate:self];

    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    if (appDelegate.firstRun){
        NSLog(@"IS FIRST RUN");
        EDViPadDocSyncService *service = [[EDViPadDocSyncService alloc]init];
        [service getAllCategories:self action:@selector(handleGetAllCategories:)];
    }
    else 
    {
        NSLog(@"NOT FIRST RUN");
        NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription
                                       entityForName:@"Categories" inManagedObjectContext:managedObjectContext];
        [fetchRequest setEntity:entity];
        NSError *errormsg;
        self.allCats = [managedObjectContext executeFetchRequest:fetchRequest error:&errormsg];
        NSLog(@"allCATS=%@",self.allCats);
        self.title = @"Categories";
    }
}

-(void)handleGetAllCategories:(id)value
{
    if([value isKindOfClass:[NSError class]])
    {
        NSLog(@"This is an error %@",value);
        return;
    }

    if([value isKindOfClass:[SoapFault class]])
    {
        NSLog(@"this is a soap fault %@",value);
        return;
    }
    NSMutableArray *result = (NSMutableArray*)value;

    NSMutableArray *categoryList = [[NSMutableArray alloc] init];
    NSMutableArray *docCount = [[NSMutableArray alloc]init];
    NSMutableArray *catIdList = [[NSMutableArray alloc]init];

    self.myData = [[NSMutableArray array] init];
    self.myDocCount = [[NSMutableArray array]init];
    self.catId = [[NSMutableArray array]init];

    for (int i = 0; i < [result count]; i++)
    {
        EDVCategory *catObj = [[EDVCategory alloc]init];
        catObj = [result objectAtIndex:i];
        [categoryList addObject:[catObj categoryName]];
        [docCount addObject:[NSNumber numberWithInt:[catObj docCount]]];
        [catIdList addObject:[NSNumber numberWithInt:[catObj categoryId]]];
    }

    self.myData = categoryList;
    self.myDocCount = docCount;
    self.catId = catIdList;
    [my_table reloadData];

    /*store data in Core Data - START*/
    NSManagedObjectContext *context = [self managedObjectContext];
    NSManagedObject *newCategory;
    for(int j=0;j<[result count];j++)
    {
        newCategory = [NSEntityDescription insertNewObjectForEntityForName:@"Categories" inManagedObjectContext:context];
        /*HOW TO STORE DATA FOR THE "CATEGORIES" OBJECT IN CORE DATA*/
    }
    /*store data in Core Data - END*/
}

I am not able to figure out how to store the data received from the wcf service to the core data object directly.I know how to store it from a text box on the screen to a core data object.eg.:-

coreDataAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSManagedObject *newContact;
newCat = [NSEntityDescription insertNewObjectForEntityForName:@"Categories" inManagedObjectContext:context];
[newCat setValue:name.text forKey:@"name"];
name.text = @"";
[context save:&error];

But this doesn’t help in my case.Any help is appreciated.

Answer 1

You are mixing networking and UI code. It is a recipe for unmaintainable code.

Your UI should be looking at Core Data and only Core Data to display its data.

Separately, and asynchronously you should be requesting data from WCF and pushing it into Core Data.

Your UI does not need to care about first run vs. subsequent run. It just looks at Core Data via a NSFetchedResultsController.

Your network code is the only part that cares about new vs. update.

Update 1

how can I achieve this? When the app is running and connected to WiFi,it has to get the latest data from the WCF service.

NSURLConnection can do async requests built-in. I generally recommend writing your networking code as NSOperation subclasses and then put them into a queue.

It appears that WCF can return XML and takes standard HTTP requests. Therefore you can write NSOperation subclasses that build your request, send it to the server and wait for a reply. When the reply comes you parse the XML and insert it into Core Data. When you save the Core Data NSManagedObjectContext your NSFetchedResultsController instances will automatically fire and allow you to update your UI.

I have several code samples that perform these feats although they are written for JSON responses as opposed to XML responses. It would not be difficult to take those examples and alter them to your needs.

You can start with this stackoverflow question and its response.