Design problems (beginner)


#1

I’m working on a medium-sized project and feel like I either:

A. Still don’t understand object-oriented programming

-or-

B. Am duplicating Ruby syntax which I’m not familiar with

First, a little background, (kept mercifully short,) I’m working on a
survey interviewing program. I’m having having trouble with hammering
classes into a structure:

Interview
Questions
Question
Answers
Contents
RHTML
Control
Answers

I’ve been told that ideally, classes like “Answers” shouldn’t know
anything about other classes like “Control”; but in practice, it’s
really convenient for Answer’s methods to talk to Control’s public
methods and vice versa.

Here’s a sexy graph:

Interview.control <=> Interview.questions.question.answers

When implementing this, to give these classes a “channel” to talk to
each other, I’ve ended up passing each “parent” object to the “child”
object at the child’s creation. Let me show you what I’m talking about:

class Question
def initialize(interview, questions)
self.interview = interview
self.questions = question

self.answers  =  Answers.new(self.interview, self.questions, self)
self.contents = Contents.new(self.interview, self.questions, self)
self.rhtml    =    RHTML.new(self.interview, self.questions, self)

end
end

In english, to be created, Question demands to be passed its Questions
“parent” and Interview “grandparent”, then passes these “ancestors” and
itself on to its children. Thankfully the children don’t have any child
objects of their own so we’re not creating any four parameter objects,
but still…

I feel like this must be the programming equivalent of eating at a fancy
restaurant with your feet. I fear I’m going to be thrown out of the
programmer’s union.

Please help! Does ruby have a better way to emphasize structure between
classes?


#2

On 1/26/06, Michael J. removed_email_address@domain.invalid wrote:

survey interviewing program. I’m having having trouble with hammering
classes into a structure:

Interview
Questions
Question
Answers
Contents
RHTML
Control
Answers

Can you give a bit more information as to what your program actually
does?

I think that you may be over classing this system

I would say you have something like:

Interview: contains collections of questions and answers
Question: constitutes a single question and associative rules such as
validation
Answer: constitutes a single response to a question, and rules such
as what
could be considered valid.

Control and Formatting tools seperate…
Consider a Question#to_rhtml method or something like that maybe?

This still might be overkill. If your questions always map to the
questions one to one, you probably don’t need a class for Answers.

I guess what I’d need to know to help is what you’d want these classes
to do.

There is almost certainly no need for Answers and Questions (the
collection classes) as an array or hash will most likely hold them
perfectly well in interview.


#3

On 1/26/06, Gregory B. removed_email_address@domain.invalid wrote:

This still might be overkill. If your questions always map to the
questions one to one, you probably don’t need a class for Answers.

s/Answers/Answer


#4

Thanks for your input, Gregory.

I’ve been doing more reading on object-oriented design today and think
you’re right, I should revamp my project structure into:

Interview
Question
Answer

And any cross-talk that currently happens between questions and answers
needs to be handled in Interview. So I’d have
Interview.compile_question, but not Interview.question(name).compile.
And I’d have Interview.answer[key].validate, but not
Interview.question(name).validate. As a bonus, it’s less typing too.


The project is a web-framework for online surveys. Already existing
open-source projects (like PHPSurveyor) lack basic functionality
required for survey research. The alternative, commercial packages,
with basic ones starting at $5,000/year for a lease – make it really
tough for people with limited means like small business consultants and
graduate students to do survey research.

So I’m trying to give back to the research community by releasing the
next version of my company’s in-house interviewing system open-source.
I’m excited about the project and the work I’ve done on it, but want the
source code to be reasonably polished too since I expect someday others
will be looking at it.

Here’s an example of my current test quesitonnaire script:

Q-INTRODUCTION
Q Thank you for your interest in this study. Once you have
completed the study, please allow up to 7-10 business days for your
[panel] credit to appear in your [panel] account. Thank you for your
time and opinions!

Q-SA1
Q Which of the following best describes your employment status? (MARK
ONE ONLY.)
X-1 Employed full-time outside of the home
X-2 Employed full-time, working from my home
X-3 Employed part-time outside of the home
X-4 Employed part-time, working from my home
X-5 Homemaker
X-6 Retired
X-7 Student
X-8 Not currently employed
post:
self.validate :required

skip ‘Q-S1’ if self.questions.current.answers.has_value? 8

Q-SA
Q Which, if any, of the following items have you purchased or ordered in
the past year for work purposes? (MARK ALL THAT APPLY.)
M-1 Business Cards
M-2 3-Ring Binders
M-3 Mailing Labels
M-4 File Folders
M-5 None of these
M-6 Not currently employed
post:
self.validate :required
self.validate :multiple, :params => [1…4, 5…6, “none of these/not
currently employed”]

skip ‘Q-SB’ if self.questions.current.answers.has_value? 2
skip ‘Q-S1’

…and so on…

Supports ERB codes too, which is kind of neat.