Why This Book?

I have been a Ruby programmer for quite a number of years, but until recently, I had been blissfully ignorant of one of Ruby’s most powerful features. One day, I saw a co-worker casually write a method that took in a block. I realized immediately that I had a major gap in my Ruby knowledge.

That incident left me unsure of my Ruby skills, so I decided to learn as much as I could about Ruby’s blocks. That pursuit also led me to Procs and lambdas.

It didn’t take long to discover that blocks, Procs, and lambdas are Ruby’s implementation of closures, hence the title of this book. The word “closure” sounds like a scary concept, and indeed, throughout my career, I avoided learning about closures. But not this time. I got my hands on every book, conference video, screencast, and blog post that even mentioned the word “closure” and dove in. This book is the distillation of everything I have learned.