How do we enumerate and modify positions array of CCsprite inside Update method? - cocos2d-iphone

Question

How do we enumerate and alter our object's position (contained in array) for each delta time?
I put some CCsprite objects inside array, then I displayed them in scene, but also I wanted to make them move with modifying update method, I failed on last part.
How do I get around this ?
#implementation GameScene
{
Hunter *_hunter;
Bird *_bird;
NSMutableArray *_arrayOfBirds;
}
-(void)update:(CCTime)delta{
CGSize viewSize = [CCDirector sharedDirector].viewSize;
float birdSpeed = 50;
for (Bird *birds in _arrayOfBirds) {
if (birds.position.x < 0) {
birds.flipX = YES;
}
if (birds.position.x > viewSize.width) {
birds.flipX = NO;
}
float distanceToMove = birdSpeed * delta;
float direction = birds.flipX ? 1 : -1;
float newX = birds.position.x + direction * distanceToMove;
float newY = birds.position.y;
birds.position = ccp(newX, newY);
}
}
-(void)addBird{
CGSize viewSize = [CCDirector sharedDirector].viewSize;
for (int i=0; i < 4; i++) {
_bird = [[Bird alloc]initWithBirdType:(i)];
_bird.position = ccp(viewSize.width * 0.5f + 30 * i , viewSize.height * 0.9f - 15* i);
[self addChild:_bird];
[_arrayOfBirds addObject:_bird];
}
}

Answer 1

You forgot to initialize your array
here (assuming ARC)
-(id) init {
if(self=[super init]) {
_arrayOfBirds = [[NSMutableArray alloc] init];
// the rest
}
return self;
}