How do I make the ball move in a certain direction? - c++

Question

I want to make my player, make the ball move in a certain direction, roughly 120 degrees up. At the moment the ball goes in al direction, but the ball goes up not down. The ball also goes at 4 different speeds.
if(CGRectIntersectsRect(BallA.frame, PlayerA1.frame)){
Y = arc4random() %5;
Y = 0-Y;
}
}
Ball movement
timer = [NSTimer scheduledTimerWithTimeInterval:0.006 target:self selector:#selector(BallMovement4) userInfo:nil repeats:YES];
-(void)BallMovement4{
[self Computer4Movement];
[self Collision4];
Ball4.center = CGPointMake(Ball4.center.x + X, Ball4.center.y + Y);
if (Ball4.center.x < 15) {
X = 0 - X;
}
if (Ball4.center.x > 305) {
X = 0 - X;
}
Please Help,
Thank You
Milan

Answer 1

It's a little unclear what you're trying to do and how your classes work, but in general, if you want to move things around, one good way to do that is to use vectors. For example, if you want the ball to move 3 pixels per frame in a given direction, the ball would have a position and a velocity vector, like this:
typedef struct Ball { // could be a class if that makes sense for your use
CGPoint position;
CGPoint velocity;
} Ball;
You'd set them to some initial value, like this:
Ball ball = { { 0.0, 0.0 }, // Ball starts at the origin
{ 1.0, 2.0 } }; // Ball starts out moving 1 pixel to the right and 2 pixels up
Then on each frame of gameplay, you'd add the velocity to the position, like this:
ball.position.x += ball.velocity.x;
ball.position.y += ball.velocity.y;
You can change the velocity, for example, when the ball hits a wall. If you're trying to simulate something real, you'd need to find the angle at which the ball hit the wall and reverse that.