Question

Here is my singleton code:

@synthesize listOfSites;

+ (id)sharedInstance
{
    static dispatch_once_t dispatchOncePredicate = 0;
    __strong static id _sharedObject = nil;
    dispatch_once(&dispatchOncePredicate, ^{
        _sharedObject = [[self alloc] init];
    });

    return _sharedObject;
}

-(id)init
{
    self = [super init];
    if (self) {
        listOfSites = [[NSMutableArray alloc] init];
    }
    return self;
}

@end

It’s pretty much textbook… however, I want to add another array, similiar to “listOfSites” (call it “listOfReadings”). The code that says “if (self)” confuses me.

How do I add another array to this code?

Answer 1

if (self) { does nothing but to verify that the [super init] has worked – and that it hasn’t return NULL or anything…

Other than that, you can do this normally, like :

• declare a listOfReadings array (as an ivar/property?)

• set it up

  listOfReadings = [[NSMutableArray alloc] init];
  

  or

  listOfReadings = [[NSMutableArray alloc] initWithObjects:nil];
  

  or (if it’s a property)

  [self setListOfReadings:[[NSMutableArray alloc] initWithObjects:nil]];
  

---

Example :

-(id) init {
    self = [super init];
    if (self) {
        listOfSites = [[NSMutableArray alloc] init];
        listOfReadings = [[NSMutableArray alloc] init];
    }
    return self;
}

after having declared the new NSMutableArray in your .h file :

NSMutableArray* listOfReadings;