NSMutableArray out of scope problem

Question

Hello all! I'm new to objective-C. I want to use NSMutableArray to store some objects i will access later.

I've got the interface:

@interface ControlWheel : RotatableObject <LeverSubject>
{
 NSMutableArray *subjectArray_;
}
-(id) initWithCWDef: (ControlWheelDef*) def;
-(void) addSubject: (id) subject;
@end

Here is the implementation:

-(id) initWithCWDef:(ControlWheelDef *)def
{
    ...
    self = [super initWithDef:&rDef];
    if (self)
    {
        subjectArray_ = [NSMutableArray arrayWithCapacity:1];
    }
    return self;
}

-(void) addSubject:(id)subject
{
    [subjectArray_ addObject:subject];
}

-(void) angleChangeCallback
{
    unsigned int count = [subjectArray_ count];
    for (unsigned int i = 0; i < count; i++)
    {
        [[subjectArray_ objectAtIndex:i] onAngleChanged:angle_];
    }
}

The problem is in angleChangeCallback function. subjectArray_ is out of scope. What i'm doing wrong?

Answer 1

It doesn't look like you have angleChangeCallback defined in your interface at the top. I see addSubject and initWithCWDef but not him.

Answer 2

arrayWithCapacity: returns an autoreleased array. You want [[NSMutableArray alloc] init];.

NSMutableArray grows as necessary, so arrayWithCapacity: isn't particularly useful, most of the time, unless you are going to fill it with a known, large number of objects.

Oh, and it's not gone out of scope; it's been collected by the autorelease pool.