Storing values in Rails session

Question

I'm taking a course on Rails, and I need to "remember" the values selected by the user across https requests, in order to filter a list.

I am supposed to do this in the session 'Hash'.

Here is my index:

def index
    #list all different values for the key ratings 
    @all_ratings = Movie.uniq.pluck(:rating) 

    #order movie list based on interaction with link from view
    @movies = Movie.order(params[:sort_param]) 

    #filter movies by rating, based on checkbox from view
    @movies = @movies.where(:rating => params[:ratings].keys) if params[:ratings].present? 

    # I intend to store here the ratings selected, and then save in session
    @selected_ratings = params[:ratings].present? ? params[:ratings] : []) 

    #It gives this error: undefined local variable or method `selected_ratings'
    session[:selected_ratings] = @selected_ratings
end

Here my view:

%h1 All Movies

= form_tag movies_path, :method => :get do
  Include:
  - @all_ratings.each do |rating|
    = rating
    = check_box_tag "ratings[#{rating}]", @all_ratings, @selected_ratings.include?(rating)
  = submit_tag 'Refresh'

%table#movies
  %thead 
    %tr
      %th{:class=> helper_class('title'), :id => ('title_header')}= link_to 'Movie Title', movies_path(sort_param: 'title')
      %th Rating
      %th{:class=> helper_class('release_date'), :id => 'release_date_header'}= link_to 'Release Date',movies_path(sort_param: 'release_date')
      %th More Info
  %tbody
    - @movies.each do |movie|
      %tr
        %td= movie.title 
        %td= movie.rating
        %td= movie.release_date
        %td= link_to "More about #{movie.title}", movie_path(movie)

And now the questions:

When I render the debug in the view, and I choose one filter (PG in this case), I get this:
```
--- !ruby/hash-with-ivars:ActionController::Parameters
elements:
  PG: G R PG-13 PG
ivars:
  :@permitted: false
```
I don't quite understand that. I guess ivars are instance variables, but I don't know why the hash is not shown in a proper {hash}, and only with the values selected.
How do I use session[:selected_ratings] to remember the filter for the movies? I mean, how do I use session as a parameter.

Maybe:
```
@movies [email protected](:rating => session[selected_ratings].keys)
```
Where can I read about how to use session, how to store, how to access and use the params stored... I have read this, and that, and also some blogposts about sessions, authentication... But I didn't manage to understand and apply to other situations than the ones described in the blog.

you need to replace session[selected_ratings]by session[:selected_ratings] — Thomas
– Thomas, Commented Jul 4, 2016 at 22:06

Tom Lord · Accepted Answer · 2016-07-04 22:14:38Z

1

Why do I get the undefined variable error if selected_ratings is defined?

@selected_ratings is defined; selected_ratings is not. What you meant to do, I think, is something like:

@selected_ratings = (params[:ratings] || session[:selected_ratings] || []) 
session[:selected_ratings] = @selected_ratings

Note that this is using a symbol, rather than an undefined variable.

Let's pretend session[selected_ratings] works, how do I use it to filter the movies? Maybe: @movies [email protected](:rating => session[selected_ratings].keys)

Well, what does @selected_ratings equal? I suspect it's probably an array of ratings, right? - Something like: ["PG", "PG-13", "R"]. In which case, ActiveRecord is clever enough and generating SQL, that you can just do something like:

@movies.where(rating: @selected_ratings)

Most importantly, where can I read about how to use session, how to store, how to access and use the params stored... I have read this, and that, and also some blogpost about sessions, authentication... But I didn't manage to understand and apply to other situation than the described in the blog.

That's a bit vague; I don't know what to suggest beyond the Rails documentation etc. for a beginners' overview. If you have a more specific question, I'd be happy to help.

answered Jul 4, 2016 at 22:14

Tom Lord

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1 Comment

cerealCode Over a year ago

Thanks a lot, I've been tinkering with the code for a while, and at some point I deleted the colon. I will change the code, and rephrase some questions.

Petr Gazarov · Accepted Answer · 2016-07-04 22:14:22Z

0

Undefined error is because you refer to variable selected_ratings which isn't defined (you defined @selected_ratings, which isn't the same thing).

To answer your second question, you can do like so:

@movies = @movies.where(:rating => session[:selected_ratings])

session hash is easy to work with. You save and retrieve values just like you would with a regular hash.

answered Jul 4, 2016 at 22:14

Petr Gazarov

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2 Comments

cerealCode Over a year ago

Thanks, I read somewhere that session is not entirely a hash, although responds like one. And when had

cerealCode Over a year ago

And when have @movies = @movies.where(:rating => session[:selected_ratings]) It does not filter at all. I think it has something to do with the session, is not storing the values properly. The debug in view says --- !ruby/hash-with-ivars:ActionController::Parameters elements: PG-13: G R PG-13 PG PG: G R PG-13 PG ivars: :@permitted: false

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