In rails 4, I am trying to access a ActiveRecord relation using multiple ids.
Ids are coming as Parameters: {"ids"=>"[55, 56]"}. In controller I am using it as User.where(:id=>params[:ids]) but this query returns zero results.
View path is like user_posts_path(:ids=>[5, 6])
Right now params[:ids].class.name is String. How to make it only as an array?
Try
User.where(id: JSON.parse(params[:ids]))
But I'd try to pass these ids as an array, not an array in a string, if possible.
Rails has a built in notation to pass arrays through the query string.
Started GET "/users?ids[]=1&ids[]=2&ids[]=3" for ::1 at 2016-08-19 12:08:42 +0200
Processing by UsersController#index as HTML
Parameters: {"ids"=>["1", "2", "3"]}
When you use some_key[]=1&some_key[]=2 notation Rails will merge all the some_key parameters into an array.
Passing a array to the path helper will generate the correct request URL.
irb(main):012:0> app.users_path(ids: [1,2,3])
=> "/users?ids%5B%5D=1&ids%5B%5D=2&ids%5B%5D=3"
# for clarity
irb(main):013:0> CGI.unescape app.users_path(ids: [1,2,3])
=> "/users?ids[]=1&ids[]=2&ids[]=3"
Using JSON.parse is just masking a bug in your application with a hacky fix.
What is most likely going wrong in your case is that the input to users_path(ids: some_variable) is a string and not an array as expected.
irb(main):014:0> CGI.unescape app.users_path(ids: "[1,2,3]")
=> "/users?ids=[1,2,3]" # this will not be treated as an array!
Something worth noting about the answers above: They do not maintain order, and they do not retrieve duplicates. To maintain order, newer Rails versions allow the following:
User.find(32, 12, 4,2,1,2,5).map(&:id)
=> [32, 12, 4, 2, 1, 5]
I'm not aware of any way to re-insert the duplicates back beyond manually re-populating the list.
