add objects to NSMutableArray when defined in .h

I am testing NSMutableArray and do not understand what i am doing wrong.

When i define "myArray" locally the [myArray addObject:@"First line"]; works but if i define it in the .h file it ends up as null.

I am using myArray to add the text of multiple selected cell's in a UITableView "didSelectRowAtIndexPath".

Could someone nice explain what i am doing wrong?

Make sure you have it like this in your .h file:

@interface YourViewController : UIViewController {

    NSMutableArray *myArray;
}

@property(nonatomic, retain) NSMutableArray *myArray;

@end

And in your .m file

@implementation YourViewController


@synthesize myArray

//make sure you release it
- (void)dealloc {
    [myArray release];
}

/*....other code..... */

/*make sure it's initialised somewhere */
- (void)viewDidLoad {
    [super viewDidLoad];
    myArray = [[NSMutableArray] alloc] init];
}   
@end

Are you just declaring an NSMutableArray in the header file? If so, it still needs to be initialized somewhere in the .m file. You could do this like so:

array = [[NSMutableArray alloc] init];
[array addObject:@"First line"];

In .h file

NSMutableArray *myArray;

In .m file

-(void)viewDidLoad
{
[super viewDidLoad];
myArray = [[NSMutableArray] alloc] init];
[myArray addObject:@"myObject"];
}