Rails: Create controller instance variables for each entry in the table

Question

In my controller's show method, I am having trouble creating an instance variable for each 'Subject' in my database. The "@pie_correct" variable works, but the problem is in the ".each" loop - I get the error "syntax error, unexpected '=', expecting keyword_end" How should I change this?

@pie_correct = TestQuestions.where(:correct => true).joins(:test).merge(Test.where(user_id: current_user))

Subject.all.each do |s|
  "@subject_ + #{s.id} + _correct" = @pie_correct.joins(:question).merge((Question.all).joins(:subject).merge(Subject.where(id: s.id)))
end

Thanks.

Chris Peters · Accepted Answer · 2014-06-24 02:48:08Z

3

You're looking for the instance_variable_set method:

Subject.all.each do |s|
  instance_variable_set "@subject_#{s.id}_correct", @pie_correct.joins(:question).merge((Question.all).joins(:subject).merge(Subject.where(id: s.id)))
end

I also believe that you don't need the pluses within your interpolated string.

answered Jun 24, 2014 at 2:48

Chris Peters

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1 Comment

user3291025 Over a year ago

Thank you, that works. I was able to access the instance variables in the view in a similar manner with instance_variable_get("@subject_#{s.id}_correct")

Richard Peck · Accepted Answer · 2014-06-24 06:26:04Z

2

System

Props to Chris Peters for his answer (which is right)

--

I wanted to raise a point about your system here. Why are you setting multiple instance variables?

At a loss for any other reason why, I'd recommend this goes against the DRY programming principles of Rails, as well as the Single Source Of Truth idea - which means you need to set data once, and use it as you wish.

I would personally set a single instance variable, and loop through that to pull the associative data.

answered Jun 24, 2014 at 6:26

Richard Peck

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2 Comments

Chris Peters Over a year ago

I'd have to agree with you. At least put all of the values into an array. When answering the question, I could only assume that @user3291025 needed it set that way for some specific reason.

user3291025 Over a year ago

Thanks Rich, I'm still learning the ropes. I have re-written the controller instance variable as: @subjects = Subject.all, and am looping through the single instance variable in the view.

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