For those who aren’t aware, ruby gems refers a way of packaging up code so it can be easily distributed for other developers to use, and a tool to help with the distributing and/or installing that code. Find out more at wikipedia.
On first glancing at this book, I wondered how you could fill a full-length book on the topic of gems. While getting the tools installed on some systems requires care, and there’s space for a couple of chapters on packaging your own libraries as gems, both topics have been covered alongside other topics in numerous volumes. What I’d missed was that contents not only covers both of those topics, but also looks at 26 different gems and explains how you might use them in your projects.
The coverage of setting up and using ruby gems at the start of the book, and on packaging and distributing your own gems at the end of the book are brief but cover the basics well enough. It might have been helpful had the latter included a little information on how to include other libraries that need to be compiled and managing the cross-platform issues that raises. Chances are anyone planning to do that is well capable of reverse-engineering a gem spec file to work out what’s needed, but it would have added some weight and helped these chapters stand out from their equivalents in other volumes.
The gems profiled cover a wide range of uses: databases, certain web services, parsing HTML, web frameworks, recurring events, PDF generation, and more. Most of them are pretty well known libraries, but few of us will have had a chance to try them all out and newcomers to the ruby community looking for some support in their projects may well find some useful tips within.
For each gem there is an introduction, some basic code samples, a lengthier code sample (with commentary) and conclusion. That repetition means this isn’t a book many will want to wade through in one go. I found that after a while I needed a break, and if reading the book it may be best to pick out a gem that particularly interests you, read the relevant section and then write some code of your own before moving on to another.
A number of times I wondered if it would be preferable to drop some of the best known gems (there are plenty of ActiveRecord examples floating around) in favour of a little more depth. In particular it would have been interesting to see a dissection of how a few of the gems work, as a sign that anyone can contribute, to see what can be learned from techniques used, and to better understand how the gems in question can be used. Such explorations might serve to break up the text a bit, as well as providing useful insights into ruby development and perhaps broadening the appeal of the book a little.
Overall, Practical Ruby Gems was a helpful read and there are a few new gems I’m going to be exploring as a result of my reading, but you may well want to take a close look before investing in a copy. You may broaden your ruby knowledge in the reading, but you’re unlikely to deepen it significantly.