There are many web pages making grand claims for the number of problems which can supposedly be solved by using vinegar. One that I've read quite often is that you can prevent your car windows from icing up. For example, here's a quote from "Chef Noah":
Prevent ice from forming on a car windshield overnight.
Coat the window with a solution of three parts white or vinegar to one part water.
I decided to try it last night. I mixed white vinegar and water in the designated proportions, put it in a misting bottle, and sprayed it all over my windscreen and rear screen. Then I went to bed safe in the knowledge that I'd be leaping happily into my car in the morning and driving off while all my neighbours stared enviously at my frost-free car.
Well, I'm not very happy to report that this morning there was absolutely no change in the amount of ice on my screen. Furthermore, I don't even think it was a particularly cold night last night - it was only about -1°C when I went out to the car in the morning. Don't these sites test their tips before posting them? So I got cold hands as usual. Bah.
I’m going to document this because it took me ages to work out, but in the end it turned out to be quite easy.
In Rails there is a useful thing called ‘flash’. Flash is a component which is automatically available in every view. Controller classes can insert a message into the flash object, and when it renders the view it can display the message. The great thing is that by default the message exists in the flash for two requests. This is so that the current request can be terminated with a browser redirect, and when the browser follows the redirect the flash message will be there waiting for it.
Read on for more details.