Creating a two dimensional array in Objective-C

Question

Whats the easiest way to declare a two dimensional array in Objective-C? I am reading an matrix of numbers from a text file from a website and want to take the data and pla

Answer 1

I'm not absolutely certain what you are looking for, but my approach to a two dimensional array would be to create a new class to encapsulate it. NB the below was typed directly into the StackOverflow answer box so it is not compiled or tested.

@interface TwoDArray : NSObject
{
@private
    NSArray* backingStore;
    size_t numRows;
    size_t numCols;
}

// values is a linear array in row major order
-(id) initWithRows: (size_t) rows cols: (size_t) cols values: (NSArray*) values;
-(id) objectAtRow: (size_t) row col: (size_t) col;

@end

@implementation TwoDArray


-(id) initWithRows: (size_t) rows cols: (size_t) cols values: (NSArray*) values
{
    self = [super init];
    if (self != nil)
    {
        if (rows * cols != [values length])
        {
            // the values are not the right size for the array
            [self release];
            return nil;
        }
        numRows = rows;
        numCols = cols;
        backingStore = [values copy];
    }
    return self;
}

-(void) dealloc
{
    [backingStore release];
    [super dealloc];
}

-(id) objectAtRow: (size_t) row col: (size_t) col
{
    if (col >= numCols)
    {
        // raise same exception as index out of bounds on NSArray.  
        // Don't need to check the row because if it's too big the 
        // retrieval from the backing store will throw an exception.
    }
    size_t index = row * numCols + col;
    return [backingStore objectAtIndex: index];
}

@end