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POC++ dynamic casting
 

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    <p>I have a main abstract class that I am provided and must create subclasses based on this class (THIS CANNOT BE MODIFIED):</p> <pre><code>class Spaceship { protected: string m_name; // the name of the ship int m_hull; // the hull strenght public: // Purpose: Default Constructor // Postconditions: name and hull strength set to parameters // -- INLINE Spaceship(string n, int h) { m_name = n; m_hull = h; } // Purpose: Tells if a ship is alive. // Postconditions: 'true' if a ship's hull strength is above zero, // 'false' otherwize. // -- INLINE bool isAlive() { return (m_hull &gt; 0); } // Purpose: Prints the status of a ship. // -- VIRTUAL virtual void status() const = 0; // Purpose: Changes the status of a ship, when hit by a // weapon 's' with power level 'power' // -- VIRTUAL virtual void hit(weapon s, int power) = 0; string getName() const { return m_name; } }; //Spaceship </code></pre> <p>So is an example of my child classes:</p> <pre><code>class Dreadnought: public Spaceship { int m_shield; int m_armor; int m_type; public: Dreadnought( string n, int h, int a, int s ): Spaceship( n, h ),m_shield( s ),m_armor(a),m_type(dreadnought){} virtual void status() const { // implementation not shown to save space } virtual void hit(weapon s, int power) { // implementation not shown to save space } int typeOf(){ return m_type; } }; </code></pre> <p>in my main code I have an dynamic array of different types of Spaceships:</p> <pre><code>Spaceship ** ships; cin &gt;&gt; numShips; // create an array of the ships to test ships = new Spaceship * [numShips]; </code></pre> <p>Then i get input from the user to declare different types of ships in this array like:</p> <pre><code>ships[0] = new Dreadnought( name, hull, armor, shield ); </code></pre> <p>my question is when I go to delete the array the correct destructor is not called, instead Spaceships is called, will this create a memory leak because the member vars "m_shield, m_armor" are not deleted and left hanging? If so is there a better way to get the type than using a var m_type and calling:</p> <pre><code>if( ships[i]-&gt;typeOf() == 0 ) delete dynamic_cast&lt;Frigate*&gt;(ships[i]); else if( ships[i]-&gt;typeOf() == 1 ) delete dynamic_cast&lt;Destroyer*&gt;(ships[i]); else if( ships[i]-&gt;typeOf() == 2 ) delete dynamic_cast&lt;Battlecruiser*&gt;(ships[i]); else if( ships[i]-&gt;typeOf() == 3 ) delete dynamic_cast&lt;Dreadnought*&gt;(ships[i]); else delete dynamic_cast&lt;Dropship*&gt;(ships[i]); </code></pre> <p>Question #2 in the Spaceship class i declared: virtual int typeOf() = 0; and commented it out, is there a way i can implement this function in the child classes without declaring in the parent class so i can use it like shown above? when i dont declare it i get the compiler error:</p> <p>error: 'class Spaceship' has no member named 'typeOf'</p> <p>I assume this again has something to do with dynamic casing.</p> <p>any help would be great,</p> <p>Thanks nat</p> <p>edit:</p> <p>to clairify my first question would i have a memory leak if I just did:</p> <p>delete ships[i];</p> <p>or should i do:</p> <p>delete dynamic_cast(ships[i]);</p> <p>to remove member vars that are only in the derived classes?</p> <p>Thnaks</p>
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    1. COI advice you to not use raw pointers, instead of Spaceship ** ships, try std::vector<std::unique_ptr<Spaceship>> ships.
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