On Sunday, February 12, 2017 at 11:29:26 AM UTC, Aida Delic wrote:
>
>
> scope :department, -> (department) { where('department == ?', department) }
> scope :year, -> (year) { where('subject.year == ?', year) }
>
> Then I called these methods in exams controller (index action) and passed
> the data:
>
> @exams = Exam.department(current_user.department) &&
> Exam.year(current_user.year)
>
> There is a problem with a scope year, it doesn't recognize subject. When I
> try to access the list of exams it says this:
> SQLite3::SQLException: no such column: subject.year: SELECT "exams".* FROM
> "exams" WHERE (subject.year == 2)
>
> But when I include subject_id: scope :year, -> (year) {
> where('Subject.find(:subject_id).year == ?', year) }
> It says there is a syntax error: SQLite3::SQLException: near "(": syntax
> error: SELECT "exams".* FROM "exams" WHERE (Subject.find(:subject_id).year
> == 2).
>
> I have tried accessing subject attributes by using delegate and to_params,
> but it didn't help. I've been googling this issue for more than 10 days,
> but I haven't been able to find a solution.
>
>
Delegate,to_params etc. are all rails things, that your database server (or
in this case sqlite) doesn't understand. You need to do a join between the
two tables, which will result in columns from both tables being available.
Rails can help you write those joins (since you have told it about your
relationships), but you should understand what those joins are. For example
you can do
Exam.joins(:subject).where(subjects: {year: 2})
Note that the joins clause use :subject (the name of the association)
whereas the where clause uses subjects (the name of the table). You can
also supply a raw fragment of sql for the join if you want a different one
to what rails generates by default (a left join in this case).
Fred
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