ruby on rails - Passing params without nil -

i want pass value of form controller should call method model searching products.

i want pass category_id , string user writes @ textfield.
pass model blank value of params (if user doesn't write on search bar or choose none category)
want save blank value cause in model, sql blank variable take "all" things. , cause if there in params , sql find thing, if there nothing in params, sql take products.

i'm not able save value of params in varibiles cause if params blank returns me error:

undefined method `[]' nil:nilclass

i hope understand me , want do. in other words , want use simple assignment pass value (even blank values) model sql query. in 1 shoot of code want program 2 cases.

here code.

in controller:

...

if params[:search]     @search_name = params[:search] end  if params[:category][:name]     @category = params[:category][:name] end   @products = product.search(@search_name,@category) 

...

in model:

def self.search(search_name,category)     ricerca = product.where("category_id = ? ",category)     ricerca = ricerca.where("title ? ", "%#{search_name}%")  end 

you can category parameters defining method like,

def category_params   params.fetch(:category, {}) end 

and, products by,

@search_name = params[:search] @category = category_params[:name] @products = product.search(@search_name, @category) 

in opinion, if making direct query on product, should like,

def product_params   params.fetch(:product, {}) end  @category = product_params[:category_id] @title = product_params[:title] @products = product.search(@category, @title) 

and in product model,

def self.search(category, title)   where("category_id = ? , title ?", category, "%#{title}%") end