Question

I am making a game in Cocos2d. I want enemies to spawn on the right and left sides of the screen, and move to a random point on the screen, then repeat. Despite my efforts, I cannot figure it out. This should be relatively easy to answer, it should look like something out of one of Ray Wenderlich’s tutorials. Some code would be nice. Thanks!

Answer 1

This is the code from ray Wanderlich tutorial..

[self schedule:@selector(addTarget) interval:2.0];

-(void)addTarget {

  CCSprite *target = [CCSprite spriteWithFile:@"Target.jpg"  
    rect:CGRectMake(0, 0, 27, 40)]; //Creating Sprite and setting rect

  // Determine where to spawn the target along the Y axis
  CGSize winSize = [[CCDirector sharedDirector] winSize]; //Get the screensize
  int minY = target.contentSize.height/2;
  int maxY = winSize.height - target.contentSize.height/2;
  int rangeY = maxY - minY;
  int actualY = (arc4random() % rangeY) + minY;

  // Create the target slightly off-screen along the right edge,
  // and along a random position along the Y axis as calculated above
  target.position = ccp(winSize.width + (target.contentSize.width/2), actualY);
  [self addChild:target];

  // Determine speed of the target
  int minDuration = 2.0;
  int maxDuration = 4.0;
  int rangeDuration = maxDuration - minDuration;
  int actualDuration = (arc4random() % rangeDuration) + minDuration;

  // Create the actions
  id actionMove = [CCMoveTo actionWithDuration:actualDuration 
    position:ccp(-target.contentSize.width/2, actualY)];
  id actionMoveDone = [CCCallFuncN actionWithTarget:self 
    selector:@selector(spriteMoveFinished:)];
  [target runAction:[CCSequence actions:actionMove, actionMoveDone, nil]];

}

minY–>position at the bottom of the screen
maxY—>position at the top of the screen.
rangeY —> the height of the screen.
actualY—>calculate the random point between bottom of the screen and top of the screen.

target.position –> setting random position for the sprite to move.

actualDuration –> getting random duration.so that the sprite moves in various time delay.

actionMove –> creating Move action.
actionMoveDone —> After completing move action,calling spriteMoveFinished to remove sprites.