When price is less than or equal to the price the user enters, display it. I can't seem to get this condition right:
conditions = ["price < ?", "%#{@params[:query]}%"] unless @params[:query].nil?
When price is less than or equal to the price the user enters, display it. I can't seem to get this condition right:
conditions = ["price < ?", "%#{@params[:query]}%"] unless @params[:query].nil?
Well, I tried that. Error because of a missing bracket, added a bracket:
NoMethodError in InventoryController#listprice
undefined method `nil' for "5000":String
So, I might be ahead of my abilities. But I just created two AJAX textboxes and linked them, one for make, the other for model. And they work great. So I added another and did the small details and then I thought I would just need to change the conditions. Thus giving me three textboxes, one for make, model and price. And you can narrow your search with each box. Enter your maximum price and it eliminates vehicles that are more expensive than that.
Thanks, JD
if you are wondering what my code is:
Inventorycontroller.rb ... def listprice
vehicles_per_page = 10
sort = case @params['sort'] when "make" then "make" when "model" then "model" when "price" then "price" when "make_reverse" then "make DESC" when "model_reverse" then "model DESC" when "price_reverse" then "price DESC" end
conditions = ["price < ?", params[:query]] unless params[:query].nil
@total = Vehicle.count(:conditions => conditions) @vehicles_pages, @vehicles = paginate :vehicles, :order => sort, :conditions => conditions, :per_page => vehicles_per_page
if request.xml_http_request? render :partial => "vehicles_list", :layout => false end
end
list.rhtml ... <form name=priceform" action="" style="display:inline;"> <label for="vehicle_price">Filter on vehicle price : </label> <%= text_field_tag("query", @params['query'], :size => 10) %> </form>
<%= image_tag("spinner.gif", :align => 'absmiddle', :border=> 0, :id => "spinner", :style=>"display: none;" ) %> </p>
<%= observe_field 'query', :frequency => 2, :update => 'table', :before => "Element.show('spinner')", :success => "Element.hide('spinner')", :url => {:action => 'listprice'}, :with => 'query' %>
conditions = ["price < ?", params[:query]] unless params[:query] == ''
Awesome! Works perfect. This is SQL language, right? Do you know where I can find a reference to learn it?
Thanks, JD
What if :query isn't passed? A better option would be:
conditions = [ 'price < ?', params[:query] ] unless params[:query].blank?
Note: Ruby methods that return boolean values typically end in a
question-mark. It's pretty. That's why the earlier example with .nil?
didn't work. The question mark wasn't referring to a question, it was
part of the code. 
Object#blank? is a helper method that Rails adds that compares against Object#nil? and Object#empty?, so when dealing with form values, it's typically the preferred method.
Even better than my suggestion above might be to validate the value, otherwise you could generate a query that makes no sense, or one that is less efficient because it involves coersion of the parameter (from a VARCHAR to a DECIMAL for example). So perhaps:
require 'bigdecimal'
class String def to_decimal self =~ /([\d\,]+(\.\d*)?|[\d\,]*\.\d+)/ $1.nil? ? nil : BigDecimal($1.gsub(/\,/, '')) end end
conditions = [ 'price < ?', params[:query].to_decimal ] unless params[:query].blank? || params[:query].to_decimal.nil?
Um - no, it's Rails Active Record which sort of does the SQL magic for you which is the sexy part of Rails.
You might want to learn more about the Ruby language and the 'Pick Axe' book is the bible for Ruby ("Programming Ruby by Dave Thomas")
Other books also of extreme usefulness would be 'Agile Web Development with Rails' by Dave Thomas and David Heinemeier Hanson and 'Ruby for Rails' by David Black
All authors frequent the list and all of these titles are available in dead tree form (most any bookseller or direct from the publishers) or from the publishers web site
Kinda. It's a mixture. ActiveRecord depends heavily on SQL certainly. You're not going to get very far without it. I'm not quite sure of a good resource to learn it. Perhaps the MySQL documentation (assuming that's your database).
The query generated in Craig's example might look like this for example:
SELECT * FROM products WHERE price > '20.0'
That forces the database to convert the VARCHAR value '20.0' into the DECIMAL value 20.0 though. Which under certain conditions could end up in execution times many times slower. So assuming ActiveRecord properly represents decimals during query generation and doesn't just turn it into a string itself, the later String#to_decimal example I posted should get around that.
