Apology for my bothering again.

I was reviewing every source code line by line and make sure that I have fully understanded them. And I found out that I could not really understand this part.

GameScene.cpp

    ....

    auto edgeBody = PhysicsBody::createEdgeBox( visibleSize, PHYSICSBODY_MATERIAL_DEFAULT, 3 );
    edgeBody->setCollisionBitmask( OBSTACLE_COLLISION_BITMASK );
    edgeBody->setContactTestBitmask( true );
    
    auto edgeNode = Node::create();
    edgeNode->setPosition( Point( visibleSize.width / 2 + origin.x, visibleSize.height / 2 + origin.y ) );
    
    edgeNode->setPhysicsBody( edgeBody );
    
    this->addChild( edgeNode );

    ....

Why we have to create a node? What for?

I tried to delete the lines with edgeNode and modified this->addChild( edgeNode ) to this->addChild( edgeBody ) , error occured.

It said physicsBody is not the child of class GameScene. So I guess it is because we have to pass the correct type?

Would you mind explaining them line by line what they do?

My appreciation!