Question

I’m developing an iPhone app.

I have the following INIT code:

shapes = [NSMutableArray arrayWithCapacity:numShapes];

After that, I want to do the following:

- (CGSize) sizeOfShapeType:(ShapeType)type{
    CGSize shapeSize = CGSizeMake(0, 0);
    if (shapes != nil) {
        for(Object2D* obj in shapes)
            if (obj.figure == type) {
                shapeSize = obj.size;
                break;
            }
    }
    return (shapeSize);
}

But I always get a EXEC_BAD_ACCESS because all shapes in shapes array are null.

How can I check if an Object2D is null?

I get the exception here:

for(Object2D* obj in shapes)

Answer 1

arrayWithCapacity returns autoreleased object, so you must retain it to make sure it won’t get deallocated prematurely:

shapes = [[NSMutableArray alloc] initWithCapacity:numShapes];

or

// .h file
@property (nonatomic, retain) NSMutableArray *shapes;
// .m file
@synthesize shapes;
// your init method
self.shapes = [NSMutableArray arrayWithCapacity:numShapes];

For the latter solution you need to declare property with retain attribute for shapes ivar.