Appendix A. Writing Backward-Compatible Code

Not everyone has the luxury of using the latest and greatest tools available. Though Ruby 1.9 may be gaining ground among developers, much legacy code still runs on Ruby 1.8. Many folks have a responsibility to keep their code running on Ruby 1.8, whether it is in-house, open source, or a commercial application. This appendix will show you how to maintain backward compatibility with Ruby 1.8.6 without preventing your code from running smoothly on Ruby 1.9.1.

I am assuming here that you are backporting code to Ruby 1.8, but this may also serve as a helpful guide as to how to upgrade your projects to 1.9.1. That task is somewhat more complicated however, so your mileage may vary.

The earlier you start considering backward compatibility in your project, the easier it will be to make things run smoothly. I’ll start by showing you how to keep your compatibility code manageable from the start, and then go on to describe some of the issues you may run into when supporting Ruby 1.8 and 1.9 side by side.

Please note that when I mention 1.8 and 1.9 without further qualifications, I’m talking about Ruby 1.8.6 and its compatible implementations and Ruby 1.9.1 and its compatible implementations, respectively. We have skipped Ruby 1.8.7 and Ruby 1.9.0 because both are transitional bridges between 1.8.6 and 1.9.1 and aren’t truly compatible with either.

Another thing to keep in mind is that this is definitely not intended to be a comprehensive guide to ...

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