Game Development Reference
In-Depth Information
We override the
init
method to add the new
setup
method that creates a new emitter
and a new physics body. We set
contactBitMask
to
playerBitmask
, since we want to
be notified when a player sprite is colliding with the enemy sprite, and we don't want
enemies to collide with each other. We set
categoryBitMask
in order to identify the
object,
collisionBitMask
to zero since we don't want our engine to handle collision
for us, and we will do it manually. We also set
affectedByGravity
to
NO
as we don't
want our enemies to fall off the screen.
The next thing we need is power-ups. Create the
ERGPowerup
class (we will use this
class to represent objects that grant shields to the player character) and set
ERGEnemy
as its
superclass
. We need to redefine the
setup
method in
ERGPowerup.m
as we
want them to do different things:
- (void) setup
{
self.emitter = [NSKeyedUnarchiver unarchiveObjectWithFile:
[[NSBundle mainBundle] pathForResource:@"powerup"
ofType:@"sks"]];
self.emitter.name = @"shieldEmitter";
self.emitter.zPosition = 50;
[self addChild:self.emitter];
self.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:20];
self.physicsBody.contactTestBitMask = playerBitmask;
self.physicsBody.categoryBitMask = shieldPowerupBitmask;
self.physicsBody.collisionBitMask = 0;
self.physicsBody.affectedByGravity = NO;
}
This is same as the previous thing, but we pick a different particle effect and another
categoryBitmask
.
After this, we need to add enemies to our scene. First, import the
ERGEnemy.h
and
ERGPowerup.h
files at the top of
ERGMyScene.m
. Second, we will need methods to
create enemies:
- (ERGEnemy *) spawnEnemy
{
ERGEnemy *temp = [[ERGEnemy alloc] init];
temp.name = @"enemy";
temp.position = CGPointMake(self.size.width + arc4random() % 800,
arc4random() % 240 + 40);
return temp;
}
