The src Directory Additional Files

You will not need to write code in the following files:

• model.h and model.cpp
• render.h and render.cpp
• route_model.h and route_model.cpp

The videos below are included to give you a better understanding of the code in those files. We will not cover model.cpp or render.cpp , as these are beyond the scope of the first course in this Nanodegree. However, we will walk through the header files for these two files, which will provide an overview of the corresponding classes and methods.

model.h

The model.h and model.cpp files come from the IO2D example code. We provide an overview of only the model.h file, as the method implementations in model.cpp file are beyond the scope of the course.

These files are used to define the data structures and methods that read in and store OSM data. OSM data is stored in a Model class which contains nested structs for Nodes, Ways, Roads, and other OSM objects. Have a look at the video above for an overview of the code in the header file.

route_model.h and route_model.cpp

These files contain classes which are used to extend the Model and Node data structures from model.h and model.cpp using class inheritance. Remember that inheritance in this case will allow you to use all of the public methods and attributes of the Model class and Node struct in the derived RouteModel and RouteModel::Node classes.

The reason for extending the existing Model class and Node struct is to include additional methods and variables which are useful for A* search. In particular, the new RouteModel::Node class now allows nodes to store the following:

• the h-value,
• the g-value,
• a "visited" flag,
• a vector of pointers to neighboring nodes.

In addition, there are now methods for

• finding neighboring Node objects of a Node,
• getting the distance to other nodes,
• finding the closest node to a given (x, y) coordinate pair.

render.h

The render.h and render.cpp files come from the IO2D example code. These take map data that is stored in a Model object and render that data as a map. We have modified these files slightly to include three extra methods which render the start point, end point, and path from the A* search. You won't need to work with these files directly, but you can watch the video above for a brief overview of the header file code.