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POC++ directed graph node with template implementation
 

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  1. POC++ directed graph node with template implementation
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    <p>I am writing program which has a multitude of Directed Graph helper functions in order to gain a deeper understanding of C++. One of the central objects is called a Node which has member functions to help with calculating travel distance between nodes. I am trying to gain a better understanding of using C++ templates in OOP design. </p> <p>Here is a quick snapshot of the Node class</p> <pre><code>class Node { friend void swap(Node &amp; first, Node &amp; second) { using std::swap; swap(first.name, second.name); } public: Node(std::string val); Node(const Node &amp; copy); Node &amp; operator = (Node copy) { swap(*this, copy); return *this; } bool operator &lt; (Node &amp; rhs) const { return (size &lt; rhs.size); } bool operator &gt; (Node &amp; rhs) const { return (size &gt; rhs.size); } bool insertEdge(Node * dest, int distToNode); // I'd like for this return type to not be tied to an int // Especially if weights were represented as floats or doubles int findTravelDistance(Node * const &amp; toNode) const; int findTravelDistance(std::queue&lt;Node *&gt; * const &amp; nodeRoute) const; // Mutators void setNodeName(const std::string nameToSet); std::string getNodeName() const; void setNodeSize(const int size); int getNodeSize() const; // Misc void toString() const; // Constants static const bool ALLOW_CIRCULAR; ~Node(); protected: private: int size; std::string name; // Here int represents the weight of the edge. I would like it to be able to be // declared as an int, float, long, or double etc... std::map&lt;Node *, int&gt; * travelEdges; }; // end class } // end namespace </code></pre> <p>As I build this class to include more functionality, I find myself struggling with how to make my functions more adaptable. For instance, look at the findTravelDistance functions.</p> <p>What I would like to do is have the return type representing weight be type agnostic and the ordered map data structure's value to be type agnostic. As it is currently implemented, a user can only declare a type int for the weight. I realize I could embark upon function overloading. But, I feel this would be too redundant and an obvious violation of the DRY principle. If I were to have to change how this function works, I would have to change it for every overload. So my gut instinct tells me I should use C++ templates. Since I am new to templates, I am struggling with where to declare it. If I make my find functions template functions and just return the generic type..</p> <pre><code>template&lt;class T&gt; T findTravelDistance(std::queue&lt;Node *&gt; * const &amp; nodeRoute) const; </code></pre> <p>That will solve my problem there. But, it doesn't fix the issue where the underlying map data structure representing edges can only hold ints. My next thought was to declared a class template..</p> <pre><code>template&lt;class T&gt; class Node { ... } </code></pre> <p>But this also seemed odd to me. This would mean declaration and initialization would look something like</p> <pre><code>Node&lt;float&gt; * n = new Node&lt;float&gt;("N"); </code></pre> <p>If I were a user of my program, I would not immediately associate Node with the float type representing edge weights.</p> <p>So what is the best or appropriate usage of a template in this case? Or is using a template even the correct path here? It is possible my class design is flawed to begin with and not very C++'esk. Any feedback here is much appreciated.</p>
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