Constructors and Destructors

Up until now, we have learned how to declare data members, how to use them in functions with a public specifier, and how to access them. Now, let's explore how to set a value to them.

In the following example, we'll declare a struct by the name of Rectangle, and set a value to it as follows:

struct Rectangle {
  int height;
  int width;
};

Rectangle rectangle;

// What will the following print function print?
std::cout << "Height: " << rectangle.height << std::endl;

This line will print a random value because we never set the value of int. The C++ rule for the initialization of basic types is that they get non-specified values.

Note

In some situations, the values of variables are set to 0 when they are not initialized. This might happen because of some details in the implementation of the operating system, the standard library, or the compiler, and the C++ standard does not guarantee it. A program will have strange bugs when it relies on this behavior...