Using an Array for collision detection

kev1953 · July 2011

I have a game where a bird files to a number of perches,
I need to detect a collision with the perch
Rather then using a load of if statements, I would like to refer to them in an array.
if (CGRectIntersectsRect(bird.frame, perch1.frame)) { }
if (CGRectIntersectsRect(bird.frame, perch2.frame)) { }
if (CGRectIntersectsRect(bird.frame, perch3.frame)) { } and so on

NSMutableArray* percharray = [NSMutableArray array];
[percharray addObject:perch1]; // Smilie is a Colon ?
[percharray addObject:perch2];
[percharray addObject:perch3];
... etc

for (int i = 0; i < num_perches; i++) {
if (CGRectIntersectsRect(bird.frame, percharray[i].frame)) { code her }
}

But I get error

struct NSMutbleArray has no member named frame

Any help please :confused:

Meredi86 · July 2011

smilie doesnt exist if you use code tags

harrytheshark · July 2011

You access objects in an NSArray with objectAtIndex:
array[i] is for C arrays.


for (int i = 0; i < num_perches; i++) {
CGRect perchFrame = [(UIView *)[percharray objectAtIndex:i] frame];
if (CGRectIntersectsRect(bird.frame, perchFrame)) { code her }
}

kev1953 · July 2011

harrytheshark, Many thanks for your post, works great :)

kev1953 · July 2011

How do I declare my NSMutableArray to be Global.
and how to use the array to set new centers for the perches :confused:

harrytheshark · July 2011

Declare it in the header file.

Can you be more specific about the second question?

kev1953 · July 2011

Declare it in the header file. Sorry if I am a total dunce. is this correct

in header file NSMutableArray *percharray;
then @property (nonatomic, retain) NSMutableArray *parcharray;

In M file in viewDidLoad

[percharray addObject:perch1];

etc
This runs OK but is not detecting a collision?

second question sorted

CGPoint perchCenter = [(UIView *)[percharray objectAtIndex:p] center];
perchCenter = newPosition;

harrytheshark · July 2011

You need to initialise the array.


- (void)viewDidLoad {
    NSMutableArray * array = [[NSMutableArray alloc] init];
    [self setPercharray:array];
    [array release];
}

You then have to release it in dealloc.

For the second part, just use setCenter: on the view.

kev1953 · July 2011

Many thanks again.

Just one last one as it still relates to the array
When a bird is shot, I wish to rotate it 180 so it hangs upsidedown.
(the birds are also in an array)

CGAffineTransform birdTransform = [(UIView *)[birdarray objectAtIndex:p] transform];
CGAffineTransform birdRotate = CGAffineTransformMakeRotation(degreesToRadians(180));
birdTransform = birdRotate;

This seems ok but does not work?

harrytheshark · July 2011

You have to actually set the transform.


[(UIView *)[birdarray objectAtIndex:p] setTransform:birdRotate];

kev1953 · July 2011

Many Many Thanks for your help :)

Howdy, Stranger!

Forums

Using an Array for collision detection

Replies