Objective C - Create a multi-dimensional array with the dimensions specified at initialisation

Question

I am trying to create a class where the width and height of a 2 dimensional array can be dynamically created at the point of initialisation with init parameters.

I h

Answer 1

Here's another way. Of course this is just for int but the code could easily be altered for other datatypes.

AOMatrix.h:

#import 


@interface AOMatrix : NSObject {

@private
    int* matrix_;
    uint columnCount_;
    uint rowCount_;
}

- (id)initWithRows:(uint)rowCount Columns:(uint)columnCount;

- (uint)rowCount;
- (uint)columnCount;

- (int)valueAtRow:(uint)rowIndex Column:(uint)columnIndex;
- (void)setValue:(int)value atRow:(uint)rowIndex Column:(uint)columnIndex;

@end

AOMatrix.m

#import "AOMatrix.h"

#define INITIAL_MATRIX_VALUE 0
#define DEFAULT_ROW_COUNT 4
#define DEFAULT_COLUMN_COUNT 4

/****************************************************************************
 * BIG NOTE:
 * Access values in the matrix_ by matrix_[rowIndex*columnCount+columnIndex]
 ****************************************************************************/
@implementation AOMatrix

- (id)init {
    return [self initWithRows:DEFAULT_ROW_COUNT Columns:DEFAULT_COLUMN_COUNT];
}

- (id)initWithRows:(uint)initRowCount Columns:(uint)initColumnCount {
    self = [super init];
    if(self) {
        rowCount_ = initRowCount;
        columnCount_ = initColumnCount;
        matrix_ = malloc(sizeof(int)*rowCount_*columnCount_);

        uint i;
        for(i = 0; i < rowCount_*columnCount_; ++i) {
            matrix_[i] = INITIAL_MATRIX_VALUE;
        }
//      NSLog(@"matrix_ is %ux%u", rowCount_, columnCount_);
//      NSLog(@"matrix_[0] is at %p", &(matrix_[0]));
//      NSLog(@"matrix_[%u] is at %p", i-1, &(matrix_[i-1]));
    }
    return self;
}

- (void)dealloc {
    free(matrix_);
    [super dealloc];
}

- (uint)rowCount {
    return rowCount_;
}

- (uint)columnCount {
    return columnCount_;
}

- (int)valueAtRow:(uint)rowIndex Column:(uint)columnIndex {
//  NSLog(@"matrix_[%u](%u,%u) is at %p with value %d", rowIndex*columnCount_+columnIndex, rowIndex, columnIndex, &(matrix_[rowIndex*columnCount_+columnIndex]), matrix_[rowIndex*columnCount+columnIndex]);
    return matrix_[rowIndex*columnCount_+columnIndex];
}
- (void)setValue:(int)value atRow:(uint)rowIndex Column:(uint)columnIndex {
    matrix_[rowIndex*columnCount_+columnIndex] = value;
}

@end