On 16 Sep 2008, at 19:34, Ad Richards wrote:
>
> Being a rails newbie, I appear to have hit a large wall.
>
> I am trying to create an online gradebook using rails, where I and
> other
> teachers at my school can record students' grades for all their
> homework
> assignments.
>
> students assessment1 assessment2 assessment3
> -------- ----------- ----------- -----------
> Bart Simpson 12 15 9
> Lisa Simpson 7 6 14
> Charlie Brown 12 14 17
>
> I would like teachers to be able to dynamically add columns for new
> assessments as they occur, and understand that this is not such a
> simple
> task.
>
This doesn't have to be very complicated. If we forget for a second
about the layout of the table, this would output students and their
grades
<% @students.each do |student|%>
<%= h student.name %>:
<% student.gradations.each do |gradation| %>
<%= h gradation.assignment.name %>: <%= gradation.grade %>
<% end %>
<% end %>
Your layout is a bit more complicated because you need to iterate over
the gradations in the same assignment order for everyone, cope with
people not having done an assignment yet etc.
I might do something like this:
in your model:
def gradation_hash
@gradation_hash ||= gradations.index_by {|g| g.assignment_id }
end
in your controller
@assignments = Assignment.find :all
@students = Student.find :all
in your view
<tr><td></td>
<% @assignments.each do |assignment| %>
<td>
<%= h assignment.name %>
</td>
<% end %>
</tr>
<% @students.each do |student| %>
<tr>
<td> <%= h student.name %> </td>
<% @assignments.each do |assignment| %>
<td>
<% if g = student.gradation_hash[assignment.id] %>
<%= h g.grade %>
<% end %>
</td>
<% end %>
</tr>
<% end >
Fred
> It is obvious that I need a join model in which to store the grades as
> there will be many students and many assignments, and each grade
> will be
> linked to both a specific assignment and specific student.
>
> So I have written my models as follows:
>
> 1. class Student
> 2. has_many :gradations
> 3. has_many :assignments, :through => :gradations
> 4. end
> 5. class Gradation
> 6. belongs_to :student
> 7. belongs_to :assignment
> 8. end
> 9. class Assignment
> 10. has_many :gradations
> 11. has_many :students, :through => :gradations
> 12. end
>
> So far so good right?
> Well I have since spent an infuriating amount of time fiddling about
> querying the models, and I can't for the life of me figure out how to
> pull out the data as in the table above. i.e. listing all the
> students'
> grades for each assignment.
> I wonder if there is somebody out there who can put me out of my
> misery.
> Or maybe I am barking up the completely wrong tree? Is there an easier
> way of doing this that I have totally overlooked?..
> Please, somebody help me. I don't want to lose any more hair over
> this.
>
> I have posted a more detailed picture of my dilemma at
> http://railspool.blogspot.com/
> --
> Posted via http://www.ruby-forum.com/.
>
> >
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