Ruby Cookbook

Recipe 17.1. Running Code Only in Debug Mode Problem You want to print out debugging messages or run some sanity-checking code, but only while you're developing your application;, not when you're running it in production. Solution ...

Recipe 17.2. Raising an Exception Credit: Steve Arneil Problem An error has occurred and your code can't keep running. You want to indicate the error and let some other piece of code handle it. Solution Raise an exception by ca...

Recipe 17.3. Handling an Exception Credit: Steve Arneil Problem You want to handle or recover from a raised exception. Solution Rescue the exception with a begin/rescue block. The code you put into the rescue clause should h...

Recipe 17.4. Rerunning After an Exception Credit: Steve Arneil Problem You want to rerun some code that raised an exception, having (hopefully) fixed the problem that caused it in the first place. Solution Retry the code that failed by e...

Recipe 17.5. Adding Logging to Your Application Problem You want to make your application log events or diagnostic data to a file or stream. You want verbose logging when your application is in development, and more taciturn logging when in pro...

Recipe 17.6. Creating and Understanding Tracebacks Problem You are debugging a program, and need to understand the stack traces that come with Ruby exceptions. Or you need to see which path the Ruby interpreter took to get to a certain lin...

Recipe 17.7. Writing Unit Tests Credit: Steve Arneil Problem You want to write some unit tests for your software, to guarantee its correctness now and in the future. Solution Use Test::Unit, the Ruby unit testing framework, from ...

Recipe 17.8. Running Unit Tests Credit: Steve Arneil Problem You want to run some or all of the unit tests you've written. Solution This solution uses the example test class PersonTest from the previous recipe, Recipe 17.7. In that scena...

Recipe 17.9. Testing Code That Uses External Resources Credit: John-Mason Shackelford Problem You want to test code without triggering its real-world side effects. For instance, you want to test a piece of code that makes an expensive net...

Recipe 17.10. Using breakpoint to Inspect and Change the State of Your Application Problem You're debugging an application, and would like to be able to stop the program at any point and inspect the application's state (variables, data ...

Recipe 17.11. Documenting Your Application Problem You want to create a set of API documentation for your application. You might want to go so far as to keep all your documentation in the same files as your source code. Solution It'...

Recipe 17.12. Profiling Your Application Problem You want to find the slowest parts of your application, and speed them up. Solution Include the Ruby profiler in your application with include 'profile' and the profiler will start tr...

Recipe 17.13. Benchmarking Competing Solutions Problem You want to see which of two solutions to a problem is faster. You might want to compare two different algorithms, or two libraries that do the same thing. Solution Use the be...

Recipe 17.14. Running Multiple Analysis Tools at Once Problem You want to combine two analysis tools, like the Ruby profiler and the Ruby tracer. But when one tool calls set_trace_func, it overwrites the trace function left by the other...