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Introducing the Constructor Critter
The Constructor Critter program demonstrates constructors. The program instantiates a new critter object, which automatically invokes its constructor. First, the constructor announces that a new critter has been born. Then, it assigns the value passed to it to the critter’s hunger level. Finally, the program calls the critter’s greeting member function, which displays the critter’s hunger level, proving that the constructor did in fact initialize the critter. Figure 8.2 shows the results of the program.
Figure 8.2
The Critter constructor initializes a new object’s hunger level automatically.
You can download the code for this program from the Course Technology website (www.courseptr.com/downloads). The program is in the Chapter 8 folder; the filename is constructor_critter.cpp.
//Constructor Critter
//Demonstrates constructors #include <iostream>
using namespace std;
class Critter
{
262 Chapter 8 n Classes: Critter Caretaker
public:
int m_Hunger;
Critter(int hunger = 0); // constructor prototype void Greet();
};
Critter::Critter(int hunger) // constructor definition
{
cout << "A new critter has been born!" << endl; m_Hunger = hunger;
}
void Critter::Greet()
{
cout << "Hi. I’m a critter. My hunger level is " << m_Hunger << ".\n\n";
}
int main()
{
Critter crit(7); crit.Greet();
return 0;
}