Question

I’ve read a lot about archiving a single array with NSKeyedArchiver. But how would I save two arrays?

I need to store/retrieve data for two view controllers within a UITabBarController. Each of the two view controllers create objects of the same custom class, but store them in a separate array for each view controller.

My current code uses a separate method for saving each array. The problem is that when archiving the second array, it overrides the first one. I can’t get them both to save. I think I either need to save the two arrays to their own file or combine the data into a single file. I’m just not sure how to write the code for this. Can anyone help??

- (void)saveFermentableIngredients
{
    NSMutableData *fermentableData = [[NSMutableData alloc] init];
    NSKeyedArchiver *fermentableArchiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:fermentableData];
    [fermentableArchiver encodeObject:self.fermentableIngredients forKey:@"FermentableIngredients"];
    [fermentableArchiver finishEncoding];
    [fermentableData writeToFile:[self dataFilePath] atomically:YES];
}

- (void)saveHopIngredients
{
    NSMutableData *hopData = [[NSMutableData alloc] init];
    NSKeyedArchiver *hopArchiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:hopData];
    [hopArchiver encodeObject:self.hopIngredients forKey:@"HopIngredients"];
    [hopArchiver finishEncoding];
    [hopData writeToFile:[self dataFilePath] atomically:YES];
}

I should mention that I’ve done the usual setup here with implementing the initWithCoder and encodeWithCoder methods. I suspect the problem is really in the code I posted above.

Answer 1

I ended up saving each array to a separate file. First I declared the two separate file paths like this:

- (NSString *)fermentableDataFilePath
{
    return [[self documentsDirectory] stringByAppendingPathComponent:@"Fermentables.plist"];
}

- (NSString *)hopDataFilePath
{
    return [[self documentsDirectory] stringByAppendingPathComponent:@"Hops.plist"];
}

Then I referenced each file path in the save methods I put in my original question. So in the first method I would have written my writeToFile method like this:

[fermentableData writeToFile:[self fermentableDataFilePath] atomically:YES];