Rails: can`t get data in callback - ruby-on-rails

Question

I try to modify data before validation, but can't: by using self.param_name will be returned nil. My code:
class Category < ActiveRecord::Base
before_validation do
logger.info ":category_parameters before: #{self.category_parameters}"
self.category_parameters = self.category_parameters.split(/,/)
logger.info ":category_parameters after: #{self.category_parameters}"
end
end
Log file:
Started PATCH "/categories/9" for 127.0.0.1 at 2014-08-16 15:13:15 +0300
Processing by CategoriesController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"7RswlNAVs26W72IY6eL56xmACbVPCZQvl7MqDMueUbg=", "category"=>{"name"=>"Computers", "url"=>"computers", "category_parameters"=>"gergewrg,rewgwerg,wergwerg"}, "commit"=>"Save", "id"=>"9"}
Category Load (0.5ms) SELECT "categories".* FROM "categories" WHERE "categories"."id" = $1 LIMIT 1 [["id", 9]]
(0.3ms) BEGIN
:category_parameters before: []
:category_parameters after: [[]]
I use PostgreSQL and :category_parameters have type array in my schema:
create_table "categories", force: true do |t|
...
t.string "category_parameters", array: true
...
end
UPD:
Controller code:
class CategoriesController < ApplicationController
before_action :set_category, only: [:show, :edit, :update, :destroy]
...
def edit
end
...
def update
respond_to do |format|
if #category.update(category_params)
format.html { redirect_to #category, notice: 'Category was successfully updated.' }
format.json { render :show, status: :ok, location: #category }
else
format.html { render :edit }
format.json { render json: #category.errors, status: :unprocessable_entity }
end
end
end
...
private
# Use callbacks to share common setup or constraints between actions.
def set_category
#category = Category.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def category_params
params.require(:category).permit(:name, :url, :category_parameters)
end
end

Answer 1

Reserved
After talking on chat, it appears the original attribute name of category_parameters was reserved by Rails for some reason (hence why the OP couldn't populate it).
The fix was to change the attribute name in the db to nested_params, the strong_params reference, and finally the attributes in the view. Here is the result:
Parameters: {"utf8"=>"✓", "authenticity_token"=>"7RswlNAVs26W72IY6eL56xmACbVPCZQvl7MqDMueUbg=", "category"=>{"name"=>"Computers", "url"=>"computers", "nested_params"=>"{123,123,123},{123,gwehrewrh,235235}"}, "commit"=>"Save", "id"=>"9"}
:nested_params before: ["123", "123", "123", "123", "gwehrewrh", "235235"]
:nested_params after: [["123", "123", "123", "123", "gwehrewrh", "235235"]]

Answer 2

Your category_parameters are not being passed as an array, they're being passed as a string.
You could try this...
params[:category][:category_parameters] = params[:category][:category_parameters].split(/,/)
params.require(:category).permit(:name, :url, category_parameters: [])
Do NOT do a before_validation record, as it will mess up your record every time you re-save it for any reason.

Answer 3

Changing your strong parameters to this format should solve your problem.
def category_params
params[:category][:category_parameters] = params[:category][:category_parameters].split!(',')
params.require(:category).permit(:name, :url, :category_parameters => [])
end