Box2D V2.x中SetAsEdge的替代方法

// Define the ground body.
    b2BodyDef groundBodyDef;
    groundBodyDef.position.Set(0, 0); // bottom-left corner

    // Call the body factory which allocates memory for the ground body
    // from a pool and creates the ground box shape (also from a pool).
    // The body is also added to the world.
    groundBody = world->CreateBody(&groundBodyDef);

    // Define the ground box shape.
    b2PolygonShape groundBox;       

    // bottom
    groundBox.SetAsEdge(b2Vec2(0,FLOOR_HEIGTH/PTM_RATIO),b2Vec2(screenSize.width*2.0f/PTM_RATIO,FLOOR_HEIGTH/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,0);

    // top
    groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO),b2Vec2(screenSize.width*2.0f/PTM_RATIO,screenSize.height/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,0);

    // left
    groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(0,0));
    groundBody->CreateFixture(&groundBox,0);

    // right
   groundBox.SetAsEdge(b2Vec2(screenSize.width*2.0f/PTM_RATIO,screenSize.height/PTM_RATIO),b2Vec2(screenSize.width*2.0f/PTM_RATIO,0));
    groundBody->CreateFixture(&groundBox,0);

Box2D v2.*中API已经移除了v1.*中的SetAsEdge方法，所以我们可以用如下方法来替换SetAsEdge方法

用b2EdgeShape 而不是 b2PolygonShape，直接用b2EdgeShape的Set方法来替换

// for the screenBorder body we'll need these values
    CGSize screenSize = [CCDirector sharedDirector].winSize;
    float widthInMeters = screenSize.width / PTM_RATIO;
    float heightInMeters = screenSize.height / PTM_RATIO;
    b2Vec2 lowerLeftCorner = b2Vec2(0, 0);
    b2Vec2 lowerRightCorner = b2Vec2(widthInMeters, 0);
    b2Vec2 upperLeftCorner = b2Vec2(0, heightInMeters);
    b2Vec2 upperRightCorner = b2Vec2(widthInMeters, heightInMeters);

    // Define the static container body, which will provide the collisions at screen borders.
    b2BodyDef screenBorderDef;
    screenBorderDef.position.Set(0, 0);
    b2Body* screenBorderBody = world->CreateBody(&screenBorderDef);
    b2EdgeShape screenBorderShape;

    // Create fixtures for the four borders (the border shape is re-used)
    screenBorderShape.Set(lowerLeftCorner, lowerRightCorner);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(lowerRightCorner, upperRightCorner);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(upperRightCorner, upperLeftCorner);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(upperLeftCorner, lowerLeftCorner);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);