Update Wait Bar While Functions Run in the Background

This example shows how to use afterEach to update a wait bar with the progress of functions running in the background.

Create a wait bar, w.

w = waitbar(0,'Please wait ...');

Set the number of iterations for your for-loop, N. Store the current number of completed iterations, 0, and the total number of iterations, N, in the UserData property of the wait bar.

N = 20;
w.UserData = [0 N];

Run a for-loop with N iterations. In each iteration, use parfeval and backgroundPool to run pause in the background for a random number of seconds. Store each Future object in an array.

for i = 1:N
    delay = rand;
    f(i) = parfeval(backgroundPool,@pause,0,delay);
end

Use the helper function updateWaitbar to update the waitbar after each Future finishes.

afterEach(f,@(~)updateWaitbar(w),0);

Use delete to close the wait bar after all the Future objects finish.

afterAll(f,@(~)delete(w),0);

Define Helper Function

Define the helper function updateWaitbar. The function increments the first element of the UserData property, then uses the vector to calculate the progress.

function updateWaitbar(w)
    % Update a waitbar using the UserData property.

    % Check if the waitbar is a reference to a deleted object
    if isvalid(w)
        % Increment the number of completed iterations 
        w.UserData(1) = w.UserData(1) + 1;

        % Calculate the progress
        progress = w.UserData(1) / w.UserData(2);

        % Update the waitbar
        waitbar(progress,w);
    end
end