Cpp - Passing Arguments to Base Constructors

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Introduction

Base class initialization can be performed during class initialization by writing the base class name followed by the parameters expected by the base class.

Demo

#include <iostream> 
class Mammal//from  ww w . ja v  a2  s.  com
{
public:
  // constructors 
  Mammal();
  Mammal(int age);
  ~Mammal();

  // accessors 
  int getAge() const { return age; }
  void setAge(int newAge) { age = newAge; }
  int getWeight() const { return weight; }
  void setWeight(int newWeight) { weight = newWeight; }

  // other member functions 
  void speak() const { std::cout << "Mammal sound!\n"; }
  void sleep() const { std::cout << "Shhh. I'm sleeping.\n"; }

protected:
  int age;
  int weight;
};

class Dog : public Mammal
{
public:
  // constructors 
  Dog();
  Dog(int age);
  Dog(int age, int weight);
  Dog(int age, int weight, int breed);
  ~Dog();

  // accessors 
  int getBreed() const { return breed; }
  void setBreed(int newBreed) { breed = newBreed; }

  // other member functions 
  void wagTail() { std::cout << "Tail wagging ...\n"; }
  void begForFood() { std::cout << "Begging for food ...\n"; }

private:
  int breed;
};

Mammal::Mammal() :
  age(1),
  weight(5)
{
  std::cout << "Mammal constructor ...\n";
}

Mammal::Mammal(int age) :
  age(age),
  weight(5)
{
  std::cout << "Mammal(int) constructor ...\n";
}

Mammal::~Mammal()
{
  std::cout << "Mammal destructor ...\n";
}

Dog::Dog() :
  Mammal(),
  breed(2)
{
  std::cout << "Dog constructor ...\n";
}

Dog::Dog(int age) :
  Mammal(age),
  breed(2)
{
  std::cout << "Dog(int) constructor ...\n";
}

Dog::Dog(int age, int newWeight) :
  Mammal(age),
  breed(2)
{
  weight = newWeight;
  std::cout << "Dog(int, int) constructor ...\n";
}

Dog::Dog(int age, int newWeight, int breed) :
  Mammal(age),
  breed(breed)
{
  weight = newWeight;
  std::cout << "Dog(int, int, int) constructor ...\n";
}


Dog::~Dog()
{
  std::cout << "Dog destructor ...\n";
}

int main()
{
  Dog my_dog2;
  Dog rover(5);
  Dog buster(6, 8);
  Dog my_dog(3, 2);
  Dog dobbie(4, 20, 3);
  my_dog2.speak();
  rover.wagTail();
  std::cout << "Yorkie is " << my_dog.getAge() << " years old\n";
  std::cout << "Dobbie weighs " << dobbie.getWeight() << " pounds\n";
  return 0;
}

Result

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