Ruby Cookbook

Recipe 7.1. Creating and Invoking a Block Problem You want to put some Ruby code into an object so you can pass it around and call it later. Solution By this time, you should familiar with a block as some Ruby code enclosed in c...

Recipe 7.2. Writing a Method That Accepts a Block Problem You want to write a method that can accept and call an attached code block: a method that works like Array#each, Fixnum#upto, and other built-in Ruby methods. Solution You don't ne...

Recipe 7.3. Binding a Block Argument to a Variable Problem You've written a method that takes a code block, but it's not enough for you to simply call the block with yield. You need to somehow bind the code block to a variable, so you can manip...

Recipe 7.4. Blocks as Closures: Using Outside Variables Within a Code Block Problem You want to share variables between a method, and a code block defined within it. Solution Just reference the variables, and Ruby will ...

Recipe 7.5. Writing an Iterator Over a Data Structure Problem You've created a custom data structure, and you want to implement an each method for it, or you want to implement an unusual way of iterating over an existing data structure. So...

Recipe 7.6. Changing the Way an Object Iterates Problem You want to use a data structure as an Enumerable, but the object's implementation of #each doesn't iterate the way you want. Since all of Enumerable's methods are based on each, this make...

Recipe 7.7. Writing Block Methods That Classify or Collect Problem The basic block methods that come with the Ruby standard library aren't enough for you. You want to define your own method that classifies the elements in an enumeration (like E...

Recipe 7.8. Stopping an Iteration Problem You want to interrupt an iteration from within the code block you passed into it. Solution The simplest way to interrupt execution is to use break. A break statement will jump out of the clos...

Recipe 7.9. Looping Through Multiple Iterables in Parallel Problem You want to traverse multiple iteration methods simultaneously, probably to match up the corresponding elements in several different arrays. Solution The SyncEn...

Recipe 7.10. Hiding Setup and Cleanup in a Block Method Problem You have a setup method that always needs to run before custom code, or a cleanup method that needs to run afterwards. You don't trust the person writing the code (possibly...