Multiple Classes Per Header

Yes, you can declare multiple classes in one header file! While the convention is one class per file, there are good reasons to group related classes together.

When to Group Classes

Good reasons to put multiple classes in one header:

• Small helper classes that are only used by the main class
• Closely related classes that always work together
• A set of classes that form a cohesive feature

Here's an example:

1// Inventory.h
2#pragma once
3
4class Item {
5public:
6  virtual int GetValue() = 0;
7};
8
9class InventorySlot {
10  Item* StoredItem{nullptr};
11  int Quantity{0};
12public:
13  void Store(Item* NewItem) {
14    StoredItem = NewItem;
15    Quantity = 1;
16  }
17  Item* GetItem() { return StoredItem; }
18};
19
20class Inventory {
21  static const int MaxSlots{20};
22  InventorySlot Slots[MaxSlots];
23public:
24  bool AddItem(Item* NewItem);
25  Item* GetItem(int SlotIndex);
26};

When to Separate Classes

You should create separate header files when:

• Classes are used independently
• Classes are large or complex
• Classes might be reused in different contexts
• Different teams work on different classes

Example of when to separate:

1// Weapon.h
2#pragma once
3class Weapon {
4  int Damage{10};
5public:
6  int GetDamage() { return Damage; }
7};

1// Character.h
2#pragma once
3#include "Weapon.h"
4
5class Character {
6  Weapon* EquippedWeapon{nullptr};
7public:
8  void EquipWeapon(Weapon* NewWeapon) {
9    EquippedWeapon = NewWeapon;
10  }
11};

Guidelines

Consider these factors:

• Will other developers expect to find these classes together?
• Does it make sense to reuse one class without the others?
• Would separating the files make the code harder to understand?
• Is the header file getting too large to manage easily?

Remember, these are guidelines, not strict rules. Use your judgment based on your specific situation.