What is BMessageRunner?

BMessageRunner is a class in Haiku OS that allows you to send messages to a target object at specified intervals. It provides a flexible and efficient mechanism for performing periodic tasks or triggering events at regular intervals within an application.

Key Features of BMessageRunner

1. Periodic Message Sending: BMessageRunner sends messages to a target object at specified intervals.
2. Thread-Safe: BMessageRunner is thread-safe, allowing multiple threads to use it simultaneously.
3. Asynchronous Communication: Messages are sent asynchronously, allowing the target object to perform tasks or respond to events without blocking.

How Does BMessageRunner Work?

The key to understanding BMessageRunner is its ability to send messages to a target object at specified intervals. Here's how it works:

1. Creation:
   1. Create a BMessageRunner object and specify the target object, the message to be sent, and the interval.
2. Start:
   1. Start the BMessageRunner, and it begins sending messages to the target object at the specified interval.
3. Message Processing:
   1. The target object (BHandler) receives the messages and processes them accordingly.
4. Periodic Execution:
   1. The BMessageRunner continues to send messages to the target object at the specified interval until stopped.

  +------------------+          +-------------------+
  |                  | 1 second |                   |
  |   BMessageRunner | -------->|      BHandler     |
  |                  |          |                   |
  +------------------+          +-------------------+
          |
          |  Sends message
          |  every 1 second
          |
          v
  +------------------+
  |                  |
  |    BMessage      |
  |      ('TASK')    |
  |                  |
  +------------------+

1 BMessageRunner is created with a 1-second interval.
2 BMessageRunner sends a message ('TASK') to the BHandler every 1 second.
3 BHandler receives the message and performs the specified task.

Example Usage of BMessageRunner

Let's say you have a BHandler object that performs a task periodically. You can use BMessageRunner to trigger the task at regular intervals:

#include <Looper.h>
#include <MessageRunner.h>
#include <Message.h>
#include <Handler.h>
#include <stdio.h>

class MyHandler : public BHandler {
public:
    MyHandler() {}

    void MessageReceived(BMessage* message) {
        switch (message->what) {
            case 'TASK':
                printf("Performing task...\n");
                break;
            default:
                BHandler::MessageReceived(message);
                break;
        }
    }
};

int main() {
    MyHandler* handler = new MyHandler();
    BMessage* message = new BMessage('TASK');

    BMessageRunner* messageRunner = new BMessageRunner(handler, message, 1000000); // 1 second interval
    messageRunner->Run();

    // Wait for user input to exit
    getchar();

    delete messageRunner;
    delete message;
    delete handler;

    return 0;
}

Explanation:

1 Creating a Handler:

MyHandler* handler = new MyHandler();

• We create a MyHandler object to handle the messages.

2 Creating a Message:

BMessage* message = new BMessage('TASK');

• We create a message with the what code 'TASK' to be sent to the handler.

3 Creating a Message Runner:

BMessageRunner* messageRunner = new BMessageRunner(handler, message, 1000000); // 1 second interval
messageRunner->Run();

• We create a BMessageRunner object with a 1-second interval and start it.