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Message Passing in C++

In C++, object-oriented programming (oops) concepts involve the use of objects, which are real-world instances of classes. Message passing in C++ is the exchange of information between two or more objects via a logical entity known as a message. In this section, we will discuss message passing in c++, examples of message passing in c++, and the Difference between message passing and method calls. Message passing refers to services that perform a simple, one-way data transfer between two programs. Message passing, like the other one-way messaging models, generally leaves the sending program unblocked.

What is Message Passing in C++?

Message passing in C++ involves passing objects or data between different parts of a program using functions, methods, or message queues. Objects communicate by sending and receiving data. A message for an object is a request for the execution of a procedure, and as such, it will invoke a function in the receiving object that produces the desired results. Message passing entails specifying the object’s name, the function’s name, and the data to be sent.

Example of Message Passing in C++

Message passing in c++ typically involves passing objects or data between different parts of a program using functions, methods, or message queues. Here’s an example of how you can use message passing in C++:

#include <iostream>
#include <string>
#include <queue>

class Message {
    std::string content;
    int priority;

    Message(std::string content, int priority) {
        this->content = content;
        this->priority = priority;

class MessageQueue {
    std::queue<Message> messages;

    void push(Message message) {

    Message pop() {
        Message message = messages.front();
        return message;

    bool isEmpty() {
        return messages.empty();

class MessageHandler {
    MessageQueue queue;

    void handleMessage() {
        while (!queue.isEmpty()) {
            Message message = queue.pop();
            std::cout << "Received message: " << message.content << std::endl;

    void sendMessage(std::string content, int priority) {
        Message message(content, priority);

int main() {
    MessageHandler handler;

    handler.sendMessage("Hello world", 1);
    handler.sendMessage("How are you?", 2);
    handler.sendMessage("Goodbye", 3);


    return 0;


Received message: Hello world
Received message: How are you?
Received message: Goodbye

In this example, the Message class represents a message to be passed between parts of the program. The MessageQueue class is a container for messages, which can be pushed and popped from the queue. The MessageHandler class is responsible for handling messages, receiving them from the queue, and processing them.
In the main() function, three messages are sent to the MessageHandler using the sendMessage() method. The handleMessage() method is then called to process the messages.

Here’s how the message passing works in detail:

  1. The main() function creates a MessageHandler object.
  2. Three messages are sent to the MessageHandler using the sendMessage() method. Each message has a string content and a priority level.
  3. The handleMessage() method is called to process the messages.
  4. The while loop runs until the message queue is empty.
  5. The pop() method is called to remove the next message from the queue.
  6. The content of the message is printed to the console.
  7. Steps 5-6 are repeated until the queue is empty.

The message queue allows messages to be stored and processed in the order they are received, while the message handler provides a way to handle messages and perform actions based on their content.

What are Message Queues in C++?

A message queue is a data structure that allows multiple processes or threads to communicate with each other by passing messages. It can be implemented using the standard library’s std::queue or a third-party library such as Boost. A message queue is a mechanism for sending and receiving messages, which are typically objects.

Difference between Message Passing and Method Call

Here we have the difference between message passing in c++ and method call:

Method call Message Passing
Method call is invoking a method on an  object Message passing is sending a message to an object
Syantax for method call is Object.method() Syntax of message passing is  Object->message()
It is procedural programming It is object-oriented programming
Execution is Synchronous Execution can be synchronous and asynchronous
Runtime efficiency is generally faster It can be slower due to message passing overhead
Method can access instance variables and state Message passing can encapsulate both data and behavior of an object
It is Supported in most language It more commonly used in OOP languages
It passed as argument It encapsulated within the message

Message passing is a fundamental concept in computer programming that involves sending data between different parts of a program or even between different programs running on other machines. Message passing can be implemented using various techniques, such as shared memory, sockets, and message queues. . Message passing in C++ can be accomplished through a variety of methods, including function calls, method calls, and message queues. The simplest form of message passing is function and method calls, in which data is passed directly between functions or methods. Message queues, on the other hand, are a better option when communication between different threads or processes is required.

Frequently Asked Questions

Here are the FAQs:

Q1. What is message passing in C++?
Ans. Message passing is a technique used in object-oriented programming to enable communication between different objects in a system. In C++, this is typically done through pointers to objects and calling member functions through those pointers.

Q2. How is message passing implemented in C++?
Ans. Message passing in C++ is typically implemented using pointers to objects and calling member functions through those pointers.

Q3. What are some common use cases for message passing in C++?
Ans. Message passing is commonly used in C++ for tasks such as interprocess communication, event handling, and distributed computing.

Q4. How do you pass messages between objects in C++?
Ans. To pass messages between objects in C++, you typically use pointers to objects and call member functions through those pointers.

Q5. Can you use message passing with templates in C++?
Ans. Yes, message passing can be used with templates in C++. This allows for more generic and reusable code that can work with different types of objects.

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