Step 7 of 8

Composition over inheritance

Inheritance means is-a: a Pistol is a Weapon. For has-a relationships, use a member instead. That's composition:

class Squad : public std::vector<Player> { };   // wrong: a squad isn't a vector
class Squad { std::vector<Player> members_; };   // right: a squad has members

Why composition is the default in professional code:

• The class controls its own interface. Inheriting from std::vector would expose erase, clear and everything else, letting callers break your rules.
• You can swap the member's type later without touching callers.
• Standard containers have no virtual destructor, so they aren't meant to be base classes at all.

Your turn: write class Squad that has a std::vector<std::string> of names, with a maximum size of 5:

• bool add(const std::string& name): false if full or already in the squad
• bool remove(const std::string& name): false if not found
• int size() const, std::string roster() const (names joined with ", ", in join order)

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