Newbie question: How to represent parent-child denormalizati


#1

I am building a relatively trivial application to try to learn my way
around Rails. I am having difficulty understanding how to navigate a
heavily denormalized hierarchy. Could someone direct me to a bare-bones
explanation of using rails to navigate database hierarchies?

I am an experienced developer. Most of my work has been desktop client
server, high performance, or server to server interprocess work in large
scale systems (8K plus users).

However, I am new to Ruby and the rails environment. Furthermore, I
have never been comfortable with html development. My idea of a perfect
screen is plain white that is sparsely populated with black text with a
single font and no effects. The default stylesheets that rails
generates are quite a bit more elaborate than I would choose to
build :o)

I am trying to build a flash-card application that contains quizzes,
questions, possible answers, and presentations, plus historical records
of users’s answers over time (quiz_instances, question_instances,
response_instances).

I have been working from Thomas and Hansson (Agile Web D. With
Rails), but I appear to be missing something in the move from the famous
“depot” example into real life. I cannot for the life of me figure out
how to navigate from parent objects (such as a quiz) to child objects.
I find a lot of what I generally consider “fluff” - adding pictures and
fonts, and tweaking positions on the screen, but I am not finding how to
build controls to navigate a hierarchy.

I could either be having issues with some web development fundamental,
or my own misunderstanding of how Rails is supposed to work.

What I have now is a skeleton that allows me to create, edit, and
destroy quizzes.

I have created the question controller, model, and views. However, I
can’t seem to be able to redirect to the list of questions from the quiz
controller. I think I understand how to nest lists once I understand
how to navigate a hierarchy.

Since questions have no content of their own, I will also need to
navigate to the presentation level to get the actual text for the
question. This is a simple hierarchical structure, with the only twist
being that a presentation (text, audio, and graphic) may be owned by
either a quiz (preamble and postamble), a question (preamble, body,
postamble), or a possible answer (body).

This chart may make it more clear (or not):

(quiz) 1…n (question) 1…n (possible answer) 1…n (presentation)
(question.preamble) 1…1 (presentation)
(question.body) 1…1 (presentation)
(question.postamble) 1…1 (presentation)
(quiz.preamble) 1…1 (presentation)
(quiz.postamble) 1…1 (presentation)

At present, I have defined quiz and question. I believe that once I
have these under control I will be able to move forward.

Thanks in advance.
David J.


#2

Hi David, you may want to look into the acts_as_tree structure


#3

I will try that as soon as I can.

Thanks!