Stuck on Cocos2d-x Basics :)

cocos2d-x C++
1

I’m writing my first project and I’m in trouble with things that someone more skilled surely knows :grin:

In my simplified scenario I have defined the layer GameLayer like this

bool GameLayer::init() {
  ...
  auto eventListener = EventListenerKeyboard::create();
  eventListener->onKeyPressed = [&](EventKeyboard::KeyCode keyCode, Event* event) {
    DoAction();
  };
  _eventDispatcher->addEventListenerWithSceneGraphPriority(eventListener, this); 
  return true;
}

For my example purposes GameLayer has 2 members:

MySprite* m_pMySprite;

and

bool m_bActionRunning;

Now the problems :sweat:

I have defined GameLayer::DoAction this way

void GameLayer::ParseInput(Direction direction) {

  if (m_bActionRunning) return;
  m_bActionRunning = true;

  CallFunc* restoreCallback = CallFunc::create([&]() { m_bActionRunning = false; });
  
  runAction(Sequence::create(
    mySprite->DoAction(),
    restoreCallback 
  ));

and MySprite::DoAction() this way

Sequence* MySprite::DoAction() {
  // update MySprite internal state
  CallFunc* updateMySpriteInternalState = CallFunc::create([&]() {
    m_PositionX = m_PositionX + 100;
  }
  // update MySprite graphical state (using m_PositionX)
  TargetedAction* updateMySpritePosition = TargetedAction::create(this, MoveTo::create(5.0f, Vec2(0, m_PositionX)));
 // returns the sequence
  return Sequence::create(
    updateMySpriteInternalState ,
    updateMySpritePosition,
    nullptr
  );
}

Since I want to keep separation logic I have defined MySprite behaviour in MySprite and not in GameLayer. GameLayer can do something on m_pMySprite returning and running the sequence object returned from m_pMySprite->DoAction(). Also at the end of the sequence GameLayer restores m_bActionRunning enabling other inputs.

Well, my questions are pretty simple

  1. is this design pattern logical or it is completely non-sense?
  2. updateMySpritePosition runs a targeted action that requires m_PositionX incremented by 100, but when the action is created m_PositionX is not incrementd because updateMySpriteInternalState is not executed yet. How can I have such variable incremented instead?
2

Hi.
The action system in cocos helps you separate sprite properties and sprite behaviour (called actions).
Then don’t combine them.
You ask question about design pattern. I think my style is a good one in cocos2d-x.
I create a discussion about design pattern for games.

3

Thank you for your time. I’m not sure to understand when you say

Basically in my example I’m returning a Sequence to update both sprite properties and sprite position (with a TargetedAction). If the caller doesn’t run the sequence, the sprite simply doesn’t change. In my head this looks good. Why should I separate sprite properties and behaviour?

4

because you can reuse this action for another sprite.
With 4 different sprites and 4 different actions you can create 4*4 = 16 behaviours. But with 4 sprites (all have own actions) you can create 4 behaviours.

5

So you are saying I should define my 4 different actions inside the GameLayer and remember to update both sprite properties and positions (with different calls)? This looks quite dangerous to me. What happens if i run the action but I forgot to update the internal state? In pattern I tried to implement such problem never happens.

6

you can update internal state of sprites with actions. (maybe custom actions)

7

Ok, I’ll think about what you are saying.
Thanks for your time :smile: