Simple example of threading in C++

Create a function that you want the thread to execute, eg:

void task1(std::string msg)

{

    std::cout << "task1 says: " << msg;

}

Now create the thread object that will ultimately invoke the function above like so:

std::thread t1(task1, "Hello");

(You need to #include <thread> to access the std::thread class)

The constructor's arguments are the function the thread will execute, followed by the function's parameters. The thread is automatically started upon construction.

If later on you want to wait for the thread to be done executing the function, call:

t1.join();
(Joining means that the thread who invoked the new thread will wait for the new thread to finish execution, before it will continue its own execution).

3 years ago

#include <thread>
#include <iostream>
#include <vector>
using namespace std;

void doSomething(int id) {
cout << id << "\n";
}

/*
* Spawns n threads
/
void spawnThreads(int n)
{
std::vector<thread> threads(n);
// spawn n threads:
for (int i = 0; i < n; i++) {
threads[i] = thread(doSomething, i + 1);
}

for (auto& th : threads) {
th.join();
}
}

int main()
{
spawnThreads(10);
}

3 years ago

When searching for an example of a C++ class that calls one of its own instance methods in a new thread, this question comes up, but we were not able to use any of these answers that way. Here's an example that does that:

Class.h

class DataManager

{

public:

    bool hasData;

    void getData();

    bool dataAvailable();

};

Class.cpp

#include "DataManager.h"



void DataManager::getData()

{

    // perform background data munging

    hasData = true;

    // be sure to notify on the main thread

}



bool DataManager::dataAvailable()

{

    if (hasData)

    {

        return true;

    }

    else

    {

        std::thread t(&DataManager::getData, this);

        t.detach(); // as opposed to .join, which runs on the current thread

    }

}

Note that this example doesn't get into mutex or locking.

3 years ago