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Discussion Questions

Meetup event

See also: Russ Olsen interview on Ruby Rogues (there were some questions about DPiR, from the beginning until about 6-7 minutes in, and perhaps later)

Preface

  • Regarding the C OOP analogy, Linus Torvalds is an OOP naysayer, but has made highly reliable (and maintainable?) code. What does this say about OOP? benjaminoakes
    • I think it means OOP is not the only way to do it. You can write poetry in French or English. danbernier
    • For the curious: Panel: Objects on Trial is supposed to be a funny but serious look at oop in general. Best point made for me is that you don't need O.O. based language to create an O.O. system. diego
  • Is it bad to use patterns as more than a vocabulary? Should they only be "rediscovered"? benjaminoakes
  • Is DRY an antipattern? Is it over-applied or often prematurely applied? benjaminoakes
  • Is YAGNI an antipattern? Is it over-applied or often prematurely applied? danbernier
  • Does Ruby hide too much complexity? Is there too much magic in, say, how mixins work? For example, the equivalent in JavaScript is as expressive, but less "magical". benjaminoakes
  • What's the equivalent in JavaScript? Something like a.extend(b)? or do you mean the prototype object model? danbernier
  • As an engineer, shouldn't you know how your plumbing works? benjaminoakes
  • Yes, but how far down? Do engineers need to understand quarks? danbernier
  • How does the problem domain affect the use of patterns? How about culture of an organization? benjaminoakes
  • I think the architecture affects it more than the problem domain. Web apps have similar patterns regardless of problem domain, and same goes for rich-client 3D simulations, rich-client GUI apps, web service layers, and language parsers. danbernier
  • How does your organization's culture view pattern use? Do they have a bad name (e.g. from being over-applied)? benjaminoakes

Chapter 1: Intro

Chapter 2: Overview of the Ruby language

This chapter is Ruby basics. If anyone has any clarifying questions, we'll be happy to clear things up.

  • Coming from statically typed languages like Java and C, I still don't fully understand how the ruby interpreter handles all @instance_variable's. How exactly does the interpreter pick up all of them? Zach
  • I'm not sure what part is unclear to you, but basically, the syntax (something like /\b@[a-z_]+\b/) makes them easy enough to recognize. The main difference is that Ruby lets you add new instance variables at run-time (see https://gist.github.com/1579738: first, f has no @bonk, then later, it does). Think of it like a hash, where the key is the instance variable's name, and you can add new keys. danbernier
  • To expand on @danbernier's explanation: are you familiar with how this is bound in JavaScript? How about this.variable = 'value'? The latter is essentially the same idea as @variable = 'value' in Ruby.

Chapter 3: Template Methods

From Wikipedia:

The control structure (inversion of control) that is the result of the application of a template pattern is often referred to as the Hollywood Principle: "Don't call us, we'll call you."

  • When have you found yourself using Template before? benjaminoakes
  • When have you wished you hadn't used Template before? benjaminoakes
  • One thing I find tricky about the Template Method pattern is picking methods to "punch out" of the template, in a way that makes sense. If you pick strictly the things that vary, it's an effective solution, but it might not be the clearest; and as the code ages & changes, you might need to refactor the lines of the template methods. Maybe this is an argument for keeping use of the template method small. I'll try to think up a good example. danbernier
  • Is Template limited in its usefulness? As @danbernier points out, it's more useful when there are fewer things that vary. The example of initialize in Ruby being a hook method is one example (only one method, but look at how much you can do with it). benjaminoakes
  • Is Ruby's Object a good example of when inheritance makes sense (in conjunction with the initialize hook)? If so, what does that mean for BasicObject?