How can I read the string in an input box while editing?

I have an input box:

this.gui.p1.name_input = uicontrol(...
    'Parent', panel,...
    'Style', 'edit',...
    'String', 'Search',...
    'FontSize', this.font.body,...
    'HorizontalAlignment', 'left',...
    'KeyPressFcn', @this.on_name_change...
);

With a callback function:

function on_name_change(this, ~, ~)
    fprintf('Name changed to %s\n', get(elem, 'String'));
end

When I type in the input box, the 'String' property doesn't get updated until I press enter or leave the input box.

For example, if the input box initially had the string 'Search', this function will print out

 Search
 Search
 Search

for every time I press a key.

The preferred behavior would be (if I pressed backspace 3 times)

 Searc
 Sear
 Sea

Update:

By adding a drawnow into the update function, the text correctly updates when I press enter. However, it doesn't work for any other keys.

function on_name_change(this, elem, ~)
    drawnow
    fprintf('changed to %s\n', get(elem, 'String_I'));
end