Detecting if Sprites are in Rect? - sprite-kit

Question

i have a tower and a monster. The tower has a SkShapeNode around it, acting as its range. And i want to check if the monster is still inside the range of the tower( i.e inside the skshape node) every frame.
i have this method which i think checks if there is anything still inside the towers' range:
-(void)update
{
[self.currentScene.physicsWorld enumerateBodiesInRect:self.towerRangeNode.frame usingBlock:^(SKPhysicsBody *body, BOOL *stop) {
if (body == nil) {
[self lostSightOfMonster];
}
}];
}
however, the [self lostSightOfMonster] method never runs.
for additional understanding, i call this method in the update method of the scene:
[self enumerateChildNodesWithName:#"Tower" usingBlock:^(SKNode *node, BOOL *stop) {
Tower *tower = (Tower *) node;
[tower update];
if (tower.hasChosenEnemy) {
[tower updateRotation];
}
}];
}
i suspect its something to do with the enumerating bodies in rect method, however i am not sure.
thanks in advance

Answer 1

I would suggest a different approach. Rather than checking if it is in contact with the sprite I would check its distance to the origin of the tower using Pythagorean theorem. I think the code would be more simple and there would be the added bonus of not having the range sprite to be visible at all times.
here is some concept code to show what I mean:
double distance;
distance = pow(enemySprite.position.x-towerSprite.position.x, 2);
distance += pow(enemySprite.position.y-towerSprite.position.y, 2);
distance = sqrt(distance);
if (distance < towerRange) {
//shoot at ememy
}
You could hypothetically put this in a for loop to check for multiple enemies as well.

Answer 2

Use this code to check for frame intersection of 2 nodes:
if(CGRectIntersectsRect(towerNode.frame, enemyNode.frame))
{
// do your thing
}
If you have more than one tower and one enemy you would use this code:
for(SKNode *towerNode in towerNodeArray)
{
for(SKNode *enemyNode in enemyNodeArray)
{
if(CGRectIntersectsRect(towerNode.frame, enemyNode.frame))
{
// do your thing
}
}
}
The above assumes you are using the physics body of the tower to check for range. Alternately you can also use some simple x and y coordinate checking like this:
if(((towerNode.position.y <= enemyNode.position.y+100) && (towerNode.position.y >= enemyNode.position.y-100)) &&
((towerNode.position.x <= enemyNode.position.x+100) && (towerNode.position.x > enemyNode.position.x+100)))
{
// do your thing
}