<!-- views/searches/new.html.erb -->
<% form_for @search do |f| %>
  <p>
    <%= f.label :keywords %><br />
    <%= f.text_field :keywords %>
  </p>
  <p>
    <%= f.label :category_id %><br />
    <%= f.collection_select :category_id, Category.all, :id, :name, :include_blank => true %>
  </p>
  <p>
    Price Range<br />
    <%= f.text_field :minimum_price, :size => 7 %> -
    <%= f.text_field :maximum_price, :size => 7 %>
  </p>
  <p><%= f.submit "Submit" %></p>
<% end %>

# models/search.rb
def products
  @products ||= find_products
end

private

def find_products
  Product.find(:all, :conditions => conditions)
end

def keyword_conditions
  ["products.name LIKE ?", "%#{keywords}%"] unless keywords.blank?
end

def minimum_price_conditions
  ["products.price >= ?", minimum_price] unless minimum_price.blank?
end

def maximum_price_conditions
  ["products.price <= ?", maximum_price] unless maximum_price.blank?
end

def category_conditions
  ["products.category_id = ?", category_id] unless category_id.blank?
end

def conditions
  [conditions_clauses.join(' AND '), *conditions_options]
end

def conditions_clauses
  conditions_parts.map { |condition| condition.first }
end

def conditions_options
  conditions_parts.map { |condition| condition[1..-1] }.flatten
end

def conditions_parts
  private_methods(false).grep(/_conditions$/).map { |m| send(m) }.compact
end