Ruby use collect/map with an attribute of a table

I have students who took 'tests', which have 5 'questions'. What I want to do is to show the max 'score' for each question for each test.

Test, Student, Question are all separate table.

class Test < ActiveRecord::Base
  has_many :students
end

class Student < ActiveRecord::Base
  belongs_to :test
  has_many :questions
end

class Question < ActiveRecord::Base
  belongs_to :students
end

The code that I have:

<% @tests.each do |test| %>
<% max_score = [] %>
    <% test.students.collect {|s| s.questions.collect {|q| max_score << q.score}}%>

    <tr>
    开发者_Python百科  <th><%= test.name %></th>
      <th><%= max_score.max %></th
    </tr>
<% end %>

However, what this shows is the max score for the whole test.

example)

Math - 95
History - 98
Physics - 100

It does not return the max for each 'question_number' 1 to 5. I want to print the max score for each question for each test.

example)

Math - 1 - 90
Math - 2 - 100
Math - 3 - 88
Math - 4 - 79
Math - 5 - 98
History - 1 - 80
History - 2 - 95
..and so on...

In the Question table it has a column named 'question_number'. I don't know how to use this attribute to get the result I want.

---

You have your models wrong. Play with this:

class Test < ActiveRecord::Base
  has_many :questions
end

class Question < ActiveRecord::Base
  belongs_to :test
  has_many :question_scores
  has_many :students, :through => :question_scores
end

class Student < ActiveRecord::Base
  has_many :question_scores
  has_many :questions, :through => :question_scores
end

class QuestionScore < ActiveRecord::Base
  belongs_to :student
  belongs_to :question
end

And the code should be something like this:

<% @tests.each do |test| %>
  <% test.questions.each do |question| %>
    test: <% test.name %>
    question: <%= question.name %>
    max score: <%= question.question_scores.maximum(:score) %>
  <% end %>
<% end %>

---

If, as your comment suggests, you're unable to alter your class structure then it's going to be a bit ugly. You can still add has_many :through to clean things up a little bit:

class Test < ActiveRecord::Base
  has_many :students
  has_many :questions, :through => :students
end

class Student < ActiveRecord::Base
  belongs_to :test
  has_many :questions
end

class Question < ActiveRecord::Base
  belongs_to :students
end

then you're going to have to nest iterators...

<% @tests.each do |test| %>
  <% 1.upto(5) do |index|
    max = test.questions.select {|q| 
            q.question_number == index }.max_by {|q| q.score } %>
    <tr>
      <td><%= test.name %></td>
      <td><%= index %></td>
      <td><%= max.score %></td>
    </tr>
  <% end %>
<% end %>

One issue with your code as it stands is that you're only outputting a <tr> once for each test. You want to do it once for each question. A better solution would be to write scopes. Something along the lines of:

class Test < ActiveRecord::Base
  has_many :students
  has_many :questions, :through => :students
end

class Student < ActiveRecord::Base
  belongs_to :test
  has_many :questions
end

class Question < ActiveRecord::Base
  belongs_to :student

  scope :max_score_by_question_number, lambda {|num| where(:question_number => num).maximum(:score) }
end

Then you could do this, which looks nicer

<% @tests.each do |test| %>
  <% 1.upto(5) do |index|
    max = test.questions.max_score_by_question_number(index) %>
      <tr>
        <td><%= test.name %></td>
        <td><%= index %></td>
        <td><%= max.score %></td>
      </tr>
    <% end %>
  <% end %>