Using form_for for nested resources in rails

on ruby-on-rails

Using object with form_for in rails in really nice things. But, it can get tricky when we need a form for nested resources. For example, we could have a @result resource, inside a @course resource. What should be done in these cases?

Rails guide gives us a hint at here. The answer from this StackOverflow question also suggests same. But it has a gotcha!

I was trying to use the same form for a smart-join table (a join table with identifying objects). The table is results and both students and courses has many of them. So, I want a two-way implementation of inputting result.

  1. Going from course side and inputting result for all of the enrolled students for that course

  2. From Student side and inputting results for all courses of that particular student.

And I want to use the same form. Here, the problem arise. Should I use form_for([@course, @result]) or form_form([@student, @result])?

The problem is solved by using just the object for the form, i.e @result and using url: option to fix route.

So, I finally used

    form_for(@result, url: {action: "create"})

Which is much more convenient. I wish, I had known this before!

Hope, this helps some other rails folks!