Part 3. Ruby dynamics

Ruby is dynamic, like human nature.

Matz, at RubyConf 2001

The phrase Ruby dynamics is almost redundant: everything about Ruby is dynamic. Variables don’t care what class of object you bind them to, which means you don’t have to (indeed, you can’t) declare their type in advance. Objects get capabilities from the classes that create them but can also branch away from their classes by having individual methods added to them. Classes and modules can be reopened and modified after their initial definitions. Nothing necessarily stays the same over the life cycle of the running program.

And those examples are just the beginning. In this last part of the book, we’ll look more deeply and widely than we yet have at the ways in which Ruby allows you to alter the execution circumstances of your program in your program.

First, in chapter 13, we’ll look at object individuation, going into the details of how Ruby makes it possible for individual objects to live their own lives and develop their own characteristics and behaviors outside of the class-based characteristics they’re “born” with. We’ll thus circle back to one of the book’s earliest topics: adding methods to individual objects. But here, equipped with the knowledge from the intervening material, we’ll zero in much more closely on the underlying mechanisms of object individuation.