Question

I have this code:
I want to store some vales in a day of the year, I set period for example 15/05/2011 to 20/05/2011

in viewDidLoad:
I store null value then I can store a value everywhere I want in the array, I’m using “sentinel values”:

appDelegate.years = [[NSMutableArray alloc] init];

for (int i = 0; i < 50; i++) // I set 50 years
{
    [appDelegate.years insertObject:[NSNull null] atIndex:i];
}

months = [[NSMutableArray alloc] init];
for (int i = 0; i < 12; i++)
{
    [months insertObject:[NSNull null] atIndex:i];
}

days = [[NSMutableArray alloc] init];
for (int i = 0; i < 31; i++)
{
    [days insertObject:[NSNull null] atIndex:i];
}

In my method:

int firstDay = 15;
int lastDay = 20;
int firstMonth = 4; 
int lastMonth = 4;
NSString *string = first; //this is the value that I want to store in the period


for (int i = firstMonth; i < lastMonth+1; i++) 
{

    for (int j = firstDay; j < lastDay+1; j++)  
    {
        NSMutableArray *values = [[NSMutableArray alloc] init];
            [values addObject:string];
            [days replaceObjectAtIndex:j withObject: values];
            [values release];
    }

    [months replaceObjectAtIndex:i withObject:days];

}

[appDelegate.years replaceObjectAtIndex:0 withObject:months]; //0 is 2011

OK, in this code I store a value in an array “values” that I store in one index of array “days” that I store in one index of array “month” that I store in one index of array “year”, it work fine; but after this, if I want store another string in array values in same position?

Example: I have another NSString *string2 = “second” and I want store this string in the same position of day then I want in same day the array values with “first” and “second”, then I can’t do “[days replaceObjectAtIndex:j withObject: values];” but what Can i do?

Answer 1

If I inferred that correctly, you are trying to store a second value at the same day, right?

If there’s no specific need for laying out your data-structure the way you currently have, I would strongly recommend you just use a plain array with 365 days. What you currently have resembles a tree structure, which is fine too but a pain to implement with arrays (and very inefficient memory wise).

You seem to forgot that once you have an array initialized at a location in your tree, you can simply append to that existing array.

Having said that, here’s my input based on your current solution:

for (int i = firstMonth; i <= lastMonth; i++) 
{
    for (int j = firstDay; j <= lastDay; j++)  // use <= instead of + 1, it's more intuitive
    {
        NSMutableArray* values = [days objectAtIndex:j];
        if (values == nil)
        {
            values = [[NSMutableArray alloc] init];
            [days insertObject:values atIndex:j];
        }
        [values addObject:string];
        [values release];
    }
    // This is unnecessary. days will never be something else than the current i-var days.
    //[months replaceObjectAtIndex:i withObject:days];
}