Question

Alright, here we go. I have a cocos2d app, and there are targets that move toward the player. When the player moves, I would like for them to slowly change their destination toward the player again, so they aren’t just moving into empty space. Is it possible to change the destination of a sprite mid-runAction?

edit:

This is the code in – (void)changeTargetDest

- (void)changeTargetDest {
    NSMutableArray* deleteArray = [[NSMutableArray alloc] init];
    for(CCSprite* s in _targets) {
        float offX = s.position.x - player.position.x;
        float offY = s.position.y - player.position.y;
        float adjustX;
        float adjustY;
        float offDistance = sqrt(powf(offX, 2.0f) + powf(offY, 2.0f));

        if(offDistance < 15) {
            [deleteArray addObject:s];

            deaths++;
            [deathLabel setString:[NSString stringWithFormat:@"Deaths: %ld", deaths]];
            if(deaths == 0)
            [kdLabel setString:[NSString stringWithFormat:@"K/D ratio: %ld.00", score]];
            else
                [kdLabel setString:[NSString stringWithFormat:@"K/D ratio: %.2f", ((float)score / (float)deaths)]];
        }

        else {
            adjustX = offX * .99;
            adjustY = offY * .99;

            CGPoint point = CGPointMake(player.position.x + adjustX, player.position.y + adjustY);

            [s setPosition:point];
        }//else

    }//for

    for (CCSprite *target in deleteArray) {

        [_targets removeObject:target];
        [self removeChild:target cleanup:YES];                                  
    }
}

This works well, except for one problem. Because the new position is calculated by just taking .99 of the previous offset, the closer the target gets to the player, the more slowly it moves. How can I make its speed constant?

Answer 1

You can stop the action and run a new action each few frames in a scheduled method.
but the better way is to compute the position of targets according to players position and use setPosition to manualy change their positions each frame in your update method.