Member Avatar for Abdel Fattah

how to make a class in c++

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  • Latest Post Latest Post by マーズ maazu

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Short, practical answer for . As pointed to reference material and recommended deeper study, here is a compact, hands-on example showing the declaration, implementation, and use of a simple C++ class, plus a few practical tips to avoid common mistakes.

// Widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include <string>

class Widget {
public:
    Widget(const std::string& name, int value = 0);
    ~Widget() = default;

    std::string name() const;
    int value() const;
    void setValue(int v);

private:
    std::string name_;
    int value_;
};

#endif // WIDGET_H
// Widget.cpp
#include "Widget.h"

Widget::Widget(const std::string& name, int value)
    : name_(name), value_(value)
{}

std::string Widget::name() const { return name_; }
int Widget::value() const { return value_; }
void Widget::setValue(int v) { value_ = v; }
// main.cpp
#include "Widget.h"
#include <iostream>

int main() {
    Widget w("example", 5);
    std::cout << w.name() << " : " << w.value() << "\n";
    w.setValue(10);
}

Quick notes and pitfalls:

  • Use header guards (or #pragma once) to avoid multiple-include errors.
  • Initialize members in the constructor initializer list (shown above).
  • Mark small getters const so they can be called on const objects.
  • If your class manages raw resources (heap memory, file handles), follow the rule of three/five: implement or =default/=delete copy/move operations appropriately, or better, use RAII and smart pointers.
  • If a class is intended as a polymorphic base, give it a virtual destructor.
  • Keep data members private and provide a minimal public interface.

This gives a starting template you can adapt. For practice, write a few small types like above, compile, and step through them in a debugger to see object lifetime and member initialization.

Recommended Answers

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Member Avatar for Slavi
commented: The Cplusplus.com web site is a great one! I use it all the time. +13
Member Avatar for マーズ maazu

It would take more than a semester to answer this one. I recommend reading 2 books:
1. Erich Gamma "Design Patterns"
2. C++ Primer 5th Ed.

Besides reading books, do get involve in opensource projects for experience in class design and OO problem solving.

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