A simple way for creating automatically sprites with compass. Guide for a rails 4+ app with assets pipeline

I took in my hands today my new book, crafting rails 4 applications

A simple and useful use of activesupport subscribe and notifications, for gathering and monitoring slow queries, slow views and many queries.

Is this really a battle for the best web development tool or something else?

Remember to always clear cache when something is very strangely wrong

Some basic reminders about assets compilation.

Different comments in haml, I forget them all the time.

Why having numericality with allow_blank and presence true at the same time? Read this article fo find out a simple trick.