How do I clear the std::queue efficiently?

Question

I am using std::queue for implementing JobQueue class. ( Basically this class process each job in FIFO manner). In one scenario, I want to clear the queue in one shot( delete all jobs from the queue). I don't see any clear method available in std::queue class.

How do I efficiently implement the clear method for JobQueue class ?

I have one simple solution of popping in a loop but I am looking for better ways.

//Clears the job queue
void JobQueue ::clearJobs()
 {
  // I want to avoid pop in a loop
    while (!m_Queue.empty())
    {
        m_Queue.pop();
    }
}

Answer 1

Yes - a bit of a misfeature of the queue class, IMHO. This is what I do:

#include <queue>
using namespace std;;

int main() {
    queue <int> q1;
    // stuff
    q1 = queue<int>(); 
}

Answer 2

A common idiom for clearing standard containers is swapping with an empty version of the container:

void clear( std::queue<int> &q )
{
   std::queue<int> empty;
   std::swap( q, empty );
}

It is also the only way of actually clearing the memory held inside some containers (std::vector)

Answer 3

'David Rodriguez', 'anon' Author of the topic asked how to clear the queue "efficiently", so I assume he wants better complexity than linear O(size of queue). Methods that you served have the same complexity: according to stl reference, operator = has complexity O(size of queue). IMHO it's because each element of queue is reserved separately and it isn't allocated in one big memory block, like in vector. So to clear all memory, we have to delete every element separately. So the straightest way to clear stl::queue is one line: while(!Q.empty()) Q.pop();