Question

Following this code:

In ViewController.m

double kk[2][2] = {{1,2},{5,6}};
if (!matrix1Col) {
    matrix1Col = [NSMutableArray array];
}

for (int i=0; i<2; i++) {
    [matrix1Row removeAllObjects];
    if (!matrix1Row) {
        matrix1Row = [NSMutableArray array];
    }

    for (int j=0 ; j<2; j++) {
        [matrix1Row insertObject:[NSNumber numberWithDouble:kk[i][j]] atIndex:j];
    }
    [matrix1Col insertObject:matrix1Row atIndex:i];
}

self.label100.text = [NSString stringWithFormat:@"%f",[[[matrix1Col objectAtIndex:0] objectAtIndex:0] doubleValue]];
self.label110.text = [NSString stringWithFormat:@"%f",[[[matrix1Col objectAtIndex:1] objectAtIndex:0] doubleValue]];
self.label101.text = [NSString stringWithFormat:@"%f",[[[matrix1Col objectAtIndex:0] objectAtIndex:1] doubleValue]];
self.label111.text = [NSString stringWithFormat:@"%f",[[[matrix1Col objectAtIndex:1] objectAtIndex:1] doubleValue]];`

I wanna show object in NSMutableArray of matrix which receive value from matrix of double in label.

And my all label must show as following ->label100 show 1 ->label110 show 5 ->label101 show 2 and ->label111 show 6

but It shows ->label100 show 5 ->label110 show 5 ->label101 show 6 and ->label111 show 6

How can I do?

Answer 1

The problem is that you’re always overwriting already inserted objects, as you insert the row many times in the same loop. That’s how I would write it:

double kk[2][2] = {{1,2},{5,6}};
NSMutableArray* matrix= [NSMutableArray new];
for(unsigned int i=0; i<2; i++)
{
    NSMutableArray* row= [NSMutableArray new];
    for(unsigned int j=0; j<2; j++)
    {
        [row addObject: @(kk[i][j]) ];
    } 
    [matrix addObject: row];
}