Rails: saving value selected in collection_select in the view

Question

I'm Rails newby, and I spent most of today trying to find an answer to my problem, but I couldn't really figure it out. I think this is a common problem a lot of people may be looking for straightforward answer, so here goes:

All I want to do is use a collection_select statement, store the selected value in a variable like @bno, and use that same variable to filter out the properties that belong to a building.

Here's my code:

<%= collection_select :property, :buildingnumber, Building.all, :streetno, :streetno, {prompt: "Building Number"},{:class => "form-control"}%> 

As I understand it from looking around SO, params[:property][:buildingnumber] should now hold my selection.

Now further down, I have this code:

<% @properties.filter_by_building(buildingnumber: Property.find(params[:property][:buildingnumber])).each do |property| %>
             <div class="col-sm-6 col-md-4">
              <div class="thumbnail relative">
                <%= image_tag property.avatar.url(:medium) %>
                <div class="caption fixedtextheight">
                  <h4>Building No: <%= property.buildingnumber%></h4><h4>Property No: <%= property.number%></h4>

                  <p><h5>Rented: <%=property.rented%></h5></p>
                  <p>
                    <a type="button" class="btn btn-default navbar-btn" href=<%= edit_property_path(property) %>>Edit</a> <%= link_to "Delete", property, method: :delete, :class=>"btn btn-default navbar-btn", data: { confirm: "Deleting this property will delete ALL the tenants, expenses, and leases associated to it."} %>   
                  </p>   
                </div>
              </div>
             </div>

          <%end%>

Here is the error I get:

NoMethodError in Properties#index Showing /Users//Desktop/JR Buildings/jrbuilding/app/views/properties/index.html.erb where line #31 raised:

undefined method `[]' for nil:NilClass Extracted source (around line #31):

                 <% @properties.filter_by_building(buildingnumber: Property.find(params[:property][:buildingnumber])).each do |property| %>

I'm confused by how I should save local variables in views, as I'm coming from a Java/Obj C background, and I want to do something very simple, which is to filter the page based on the value the user selects in a collection_select. Also I need to figure out how to update the page somehow.

Anyway helpful tips much appreciated, thank you in advance!

Also want to show you my filter_by_building code in my property model:

def self.filter_by_building(opts={})
    buildingNo = opts[:buildingnumber]
    building = Building.arel_table

    self.where(:buildingnumber => buildingNo)
end

Thanks so much!