Initialize a session var as array in Rails 3

I need to initialize a session var as array. Where i do that?

when i try to do this:

session[:complains_id] << params[:id]

i get this message

You have a nil object when you didn't expect it开发者_运维技巧! You might have expected an instance of Array. The error occurred while evaluating nil.<<

I know that i have to initialize the var but i dont know where.

Thanks!

Just do:

  (session[:complains_id] ||= []) << params[:id]

Which is saying:

1. if session[:complains_id] returns nil, set it to [].

2. Append params[:id] to session[:complains_id]

Demo:

ruby-1.9.2-p136 :007 > (session[:complains_id] ||= []) << 5
 => [5] 
ruby-1.9.2-p136 :008 > (session[:complains_id] ||= []) << 3
 => [5, 3] 
ruby-1.9.2-p136 :009 > (session[:complains_id] ||= []) << 1
 => [5, 3, 1]