How to add strings to an NSMutableArray

Question

I am trying to select multiple UITableViewCells, it is working fine, but I can't add strings to my NSMutableArray.

I am using this code, and my log always is (null):

self.mutarray = [[NSMutableArray alloc] init];
[self.mutarray addObject:path]; //path is an NSString
NSLog(@"%@", self.mutarray);

It must add the path of the UITableViewCell to the NSMutableArray, is that even possible?

Oh, and I am calling this in - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

You never actually created the array. Declaring the array pointer does not create the array. — Hot Licks
– Hot Licks, Commented Aug 25, 2013 at 18:22

Apoorv · Accepted Answer · 2013-08-25 22:28:55Z

3

As per your comments "it shows only the new added string, but not all strings.". This is because you are allocating NSMutable Array in the delegate method of table view. Everytime you hit the cell a new array is get allocated.

Either allocate your "mutarray" array in ViewDidLoad

Or

Only allocate it if it is nil or empty.

  if(!self.mutarray)
   self.mutarray = [[NSMutableArray alloc] init];

answered Aug 25, 2013 at 22:28

Apoorv

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3 Comments

idoodler Over a year ago

OK, I added self.mutarray = [[NSMutableArray alloc] init]; to -(void)viewDidLoad, but it still only shows the newest string, and not the newest and the other, previews strings

Apoorv Over a year ago

can you please post your updated code in the - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

idoodler Over a year ago

OMG, I fixed it, sorry for that. You were completely right, I forgot to delete the alloc init path from the didSelectRowAtIndexPath method. Its 1:09 here, so I think I have to sleep, so I can think better:) Thanks again!

3lvis · Accepted Answer · 2013-08-25 18:31:21Z

2

It seems that you haven't initialized your array. A good practice for properties is using something called lazy initialization.

Add this method.

- (NSMutableArray *)mutarray
{
    if (!_mutarray) {
        _mutarray = [[NSMutableArray alloc] init];
    }
    return _mutarray;
}

So every time you request the array, the accessor will make sure that the object is created before returning it. This is a good way of defensive programming.

answered Aug 25, 2013 at 18:31

3lvis

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1 Comment

idoodler Over a year ago

Sorry, I had it initialized and allocated, I just forgot to add it, and it was in the if statement above. Now it shows only the new added string, but not all strings.

Abdullah Shafique · Accepted Answer · 2013-08-25 18:18:26Z

1

You have to alloc/init before adding any objects:

if(!mutarray)mutarray = [[NSMutableArray alloc]init];
[self.mutarray addObject:path];

answered Aug 25, 2013 at 18:18

Abdullah Shafique

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1 Comment

idoodler Over a year ago

Sorry, I had it initialized and allocated, I just forgot to add it, and it was in the if statement above. Now it shows only the new added string, but not all strings.

Peter Grundner · Accepted Answer · 2013-08-25 22:24:54Z

0

Have you tried to add a copy of the path? Since UITableViewCells are resused, maybe the problem resides to this?

[self.mutarray addObject:[path copy]];

answered Aug 25, 2013 at 22:24

Peter Grundner

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1 Comment

Peter Grundner Over a year ago

stupid question: are you doing the init and alloc stuff in didSelectRowAtIndexPath as well? If yes, try to do this part of your code in viewWillAppear.

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