Constructor in Abstract Class

Yes, you can have a constructor in an abstract class. Although you cannot instantiate an abstract class directly, its constructors are called when a derived class object is created.

The purpose of the constructor in an abstract class is to initialize common data members and perform any setup required for the base part of the derived objects.

Here’s an example:

1#include <iostream>
2#include <string>
3
4// Abstract base class with a constructor
5class Character {
6public:
7  Character(const std::string& name)
8  : Name(name) { 
9    std::cout << "Character created: "
10      << Name << "\n";
11  }
12
13  virtual std::string GetName() = 0;
14
15protected:
16  std::string Name;
17};
18
19class Warrior : public Character {
20public:
21  Warrior(const std::string& name)
22    : Character(name) {}  
23
24  std::string GetName() override {
25    return Name;
26  }
27};
28
29int main() {
30  Warrior warrior("Aragon");
31  std::cout << "Warrior's name: "
32    << warrior.GetName() << "\n";
33}

1Character created: Aragon
2Warrior's name: Aragon

In this example:

• Character is an abstract class with a constructor that initializes the Name member and prints a creation message.
• Warrior is a concrete class that inherits from Character and calls the base class constructor to initialize the Name member.
• When a Warrior object is created, the Character constructor runs first, initializing common members and performing any necessary setup.

Purpose of Constructors in Abstract Classes

1. Initialize Common Data Members: Constructors in abstract classes can initialize data members that are common to all derived classes, reducing redundancy and ensuring consistency.
2. Setup and Validation: They can perform initial setup and validation tasks that are required before the derived class constructors run.
3. Resource Management: Constructors in abstract classes can acquire resources that are needed by derived classes, ensuring proper resource management and initialization.

Using constructors in abstract classes helps ensure that all derived objects are correctly initialized and adhere to a common setup routine, even though the abstract class itself cannot be instantiated.