在一次Rails迁移中有多个表-如何命名

Question

rails, as I understand it, provides all sorts of benefits if you follow its naming conventions. Thus, in the Expect model I just created, I also got all the similarily named views and controllers, and in the migration

class CreateExpects < ActiveRecord::Migration
  def self.up
    create_table :expects do |t|

I note that it creates the table "expects" in this migration automatically, and I assume some benefits flow from that. However, what if I want to create multiple tables in this migration

For example, I am building a really simple app where students are asked two questions,

The students will be asked two questions on a form

"Which courses do you think students will likely fail?" (Check all that apply)
Math, English, French, Science

"Which courses do you think students will likely pass?" (check all that apply)
Math, English, French, Science

but the suggestions from people for structuring the database is to create several tables, and since the tables will also have different names, how do I deal with the fact that I'm no longer conforming to the rails conventions

For example, if the two questions are asked in one form which is in views/expects/new.html.erb (and _form), how do I make sure the data goes into the right table for each question? and then pull it out all together in the othe rpage where I show the data?

Answer 1

I don't think I fully understand what you are asking, but I think I can help you just based on your problem. This is what your database set up should look like.

1. Create a table called student. You can use generate model command.

   rails generate model student

2. Go in to your migration folder (db/migrate) and look for the student migration file.

3. Add these lines in your migration file. Note that you could have used some association between student and subjects to set up the database, but for a simple app like this, I wouldn't bother.

   t.boolean :firstanswer_math
   t.boolean :firstanswer_english
   t.boolean :firstanswer_french
   t.boolean :firstanswer_science
   t.boolean :secondanswer_math
   t.boolean :secondanswer_english
   t.boolean :secondanswer_french
   t.boolean :secondanswer_science
   

4. In the view, associate check box with each subject for each question.

   FIRST QUESTION
   <%= form.check_box :firstanswer_math =>
   <%= form.check_box :firstanswer_english =>
   ...

5. Of course, you'd need appropriate methods in Controller file for student, but I'll omit that step.

Let me know if I adequately answered your question.

---

First Edit

• I can call student.firstanswer_math but I can't call firstanswer_math.student do you know how I'd set up the migrations to create that kind of reversible method call flexibility?

There isn't such flexibility. You have to go in this order, object.attribute .

• do I need a has_many_through?

Nope, you should be find without it. You need has_many type of association when you want to associate two models with two different database tables. In our case, the app can be easily set up in one model and several attributes. So having one table is perfectly fine.

• even though you might not think it ideal for the purpose of this simple app, since I'm learning I'm wondering if using a more complex structure that allows calling student.firstanswer_math AND firstanswer_math.student might allow me some more flexibility in terms of data that I crunch and present different ways.

I think now I understand why you bring up "firstanswer_math.student". Are you trying to find students with firstanswer_math set to true or something? If you want to do that you can use find method on student. So for example,

@students = Student.find_all_by_firstanswer_math( true )

• I'm still learning rails so I'm really just playing around, but if you can suggest the best structure (first recommendation very good) for this more complex set up, then please do

I wouldn't say I'm a Ruby on Rails expert, but I think most Ruby on Rails developers would probably go for my implementation for your problem.