In development of a new, greenfield application I had flash messages popping up twice: once for the current page, and then again on the next page. It turns out I was using flash[]= and then rendering within the same action. As flash[]= is designed to carry over to the next action (i.e. after you redirect, a new action is performed) it was showing up again. The solution: flash.now[]=. This hash is cleared after the current action. The following code illustrates when to use each:
def create_application
#do work
if it_worked?
flash[:notice] = "Great success!"
redirect_to @cash
else
flash.now[:error] = "Let's try that again"
render :action => "new"
end
end
The flash[:notice] must be carried over to the action that handles the @cash path (following to the redirect), whereas the flash.now[:error] will be shown for the current action (even though it renders a different view) and should not be carried over to the next action.
It seems somewhat strange to me that I’m just discovering this now. I suppose that as I learn more about Rails and web applications in general, I adjust my techniques and start experimenting with new ones (that aren’t always better). The fact that flash[]= carries over to the next action and flash.now[]= doesn’t has only come into play now that I’m using flash as more of a central messaging system than just the standard notices from scaffolds.
