Classes: A Simple Example

main()

{

// Note: C++ doesn’t require the ‘struct’

// and ‘class’ keywords in declarations.

counter apples;

counter oranges;

counter *pointer_to_counter = NULL;

counter array_of_counters[10];

int x = 5;

// Access a class member just like

// a structure member in C.

apples.some_data = x;

// And call functions too!

apples.set_counter(10);

apples.increment_counter();

apples.increment_counter();

oranges.set_counter(5);

oranges.decrement_counter();

printf(“%d apples and %d oranges!\n”,

apples.query_counter(), // 12

oranges.query_counter()); // 4

}

// Note this C++ comment. In C++,

// everything from the ‘//’ to the end

// of the line is a comment.

class counter {

public: // ignore this for now

int some_data;

char some_other_data[100];

int i;

// Complete (defined) functions.

void increment_counter() { i++; }

void decrement_counter() { i--; }

int query_counter() { return i; }

// Note, “void” no longer needed for

// functions that take no arguments.

// Just a function prototype; body

// must be defined elsewhere

void set_counter(int new_value);

};

// Prototype must match. Note “::”!!

void counter::set_counter(int new_value)

{

i = new_value;

}

Previous slide

Next slide

Back to first slide

View graphic version