How to call a func only one time in ccTouchMove?

cocos2d-x C++
#1

bool GameBoard::ccTouchMove(cocos2d::CCTouch pTouch, cocos2d::CCEventpEvent){
pos = convertTouchToNodeSpace(pTouch);
if (pos.x > 100){
exchangeCells();
}
}
Hello ,everybody!
What can I do if want to call exchangeCells() only one time when pos.x > 100!?

#2

Create a Boolean flag and check for it

#3

just as Bengigi saying.
in the frant of your code , add a flag like this: bool flag = true;
then in your Move method:
if(pos.x > 100 && flag == true)
{
exchangeCells();
flag = false;
}

any methods somebody has?