Trying to get user input to move sprite in Cocos2D-X - c++

Question

I'm trying to make user input of WASD move a sprite around in Cocos2D-X. I'm pretty sure I'm doing everything correct but it gives me this error:
expression must be a modifiable lvalue.
Here is my code (Note: I'm new to Cocos2D-X, so it might be a bit messy)
float playerX = visibleSize.width / 2 + origin.x;
float playerY = visibleSize.height / 2 + origin.y;
auto player = Sprite::create("sprites/player.png");
if (player == nullptr)
{
problemLoading("'sprites/player.png'");
}
else
{
// position the sprite on the center of the screen
player->setPosition(Vec2(playerX, playerY));
// add the sprite as a child to this layer
this->addChild(player, 0);
}
// Keyboard events
auto keyboardListener = EventListenerKeyboard::create();
keyboardListener->onKeyPressed = [playerX, playerY](EventKeyboard::KeyCode keyCode, Event* event)
{
switch (keyCode)
{
case EventKeyboard::KeyCode::KEY_W:
playerY += 5.0f;
break;
case EventKeyboard::KeyCode::KEY_A:
playerX -= 5.0f;
break;
case EventKeyboard::KeyCode::KEY_S:
playerY -= 5.0f;
break;
case EventKeyboard::KeyCode::KEY_D:
playerX += 5.0f;
break;
case EventKeyboard::KeyCode::KEY_ESCAPE:
Director::getInstance()->end();
break;
}
};
_eventDispatcher->addEventListenerWithSceneGraphPriority(keyboardListener, this);
There is four of the error and they all point to a different playerX/Y +=/-= 5.0f

Answer 1

Try to use mutable specifier(which allows lambdas body to modify the objects captured by copy, and to call their non-const member functions):
float playerX = visibleSize.width / 2 + origin.x;
float playerY = visibleSize.height / 2 + origin.y;
auto player = Sprite::create("sprites/player.png");
if (player == nullptr)
{
problemLoading("'sprites/player.png'");
}
else
{
// position the sprite on the center of the screen
player->setPosition(Vec2(playerX, playerY));
// add the sprite as a child to this layer
this->addChild(player, 0);
}
// Keyboard events
auto keyboardListener = EventListenerKeyboard::create();
// add mutable specifier
keyboardListener->onKeyPressed = [playerX, playerY, player](EventKeyboard::KeyCode keyCode, Event* event) mutable
{
switch (keyCode)
{
case EventKeyboard::KeyCode::KEY_W:
playerY += 5.0f;
break;
case EventKeyboard::KeyCode::KEY_A:
playerX -= 5.0f;
break;
case EventKeyboard::KeyCode::KEY_S:
playerY -= 5.0f;
break;
case EventKeyboard::KeyCode::KEY_D:
playerX += 5.0f;
break;
case EventKeyboard::KeyCode::KEY_ESCAPE:
Director::getInstance()->end();
break;
}
player->setPosition(playerX, playerY);
};
_eventDispatcher->addEventListenerWithSceneGraphPriority(keyboardListener, this);