Question

My URL is as follows:

http://localhost:3000/movies?ratings[PG-13]=1&commit=Refresh

I’m experimenting evaluating URL params and am unsure why this works the way is does. In my controller I evaluate the parameters and build an array as follows:

In my View I use the following debug statement to see what gets placed into @selected_ratings

=debug(@selected_ratings)

In my controller I have tried two statements.

Test one returns the following, this should work?

@selected_ratings = (params["ratings[PG-13]"].present? ? params["ratings[PG-13]"] : "notworking")

output: notworking

However if I use the following ternary evaluation n my controller:

@selected_ratings = (params["ratings"].present? ? params["ratings"] : "notworking")

output:!map:ActiveSupport::HashWithIndifferentAccess 
  PG-13: "1"

Why will my evaluation not find the literal params["ratings[PG-13]"]?

Answer 1

Rails parses string parameters of the form a[b]=c as a hash [1] where b is a key and c is its associated value: { :a => { :b => "c" } }.

So the url http://localhost:3000/movies?ratings[PG-13]=1&commit=Refresh will result in the hash:

{ :ratings => { :'PG-13' => "1"}, :commit => "Refresh" }

In your first assignment, you check if params["ratings[PG-13]"] is present, and since it is not, it returns “notworking”. In the second case, you check if params["ratings"] is present, and it is, so it returns params["ratings"], which is a hash with the key PG-13 and value "1".

[1] Or rather, a HashWithIndifferentAccess, a special kind of hash that converts symbol and string keys into a single type.