CODEWITHSUNDEEP
ruby-on-railssearchassociationshas-many
Niko Efimov
Niko Efimov

Reputation: 2213

Rails: How to implement search through association

Original Question

My app deals with "Machines". Machines have specifications, written as many "Specs". Each of those Specs contains a reference to "Spec_Field" (Fields such as "Weight", "Height", "Capacity", etc), and a value.

Class Machine
  has_many :specs
  has_many :spec_fields, :through => :specs

Class Spec
  belongs_to :machine
  belongs_to :spec_field

What I want to do is to have a Search function in the #show action for each Machine, where a user checks off the Specs that he wants to match ("Yes, length 50 is what I need, and capacity 500 is perfect, I don't care for width"), and clicks "Find Similar", which would then find all Machines with similar Specs.

I assume I'll need a model for Search, similar to the following screencast: http://railscasts.com/episodes/111-advanced-search-form-revised?autoplay=true

In the #show action for a Machine, I will then need to go through this Machine's Specs, and add them to the "Search" instance. So does that mean a "Spec" also needs to belong to "Search"?

I just can't wrap my mind around how to organize everything in my case. Any help is appreciated!

Database Schema

Machines:

t.string   "title"
t.text     "description"
t.datetime "created_at",                      :null => false
t.datetime "updated_at",                      :null => false
t.string   "status"
t.integer  "category_id"
t.string   "manufacturer"
t.string   "model"
t.string   "serial"
t.string   "year"
t.string   "location"

Specs:

t.integer  "machine_id"
t.integer  "field_id"
t.text     "value"
t.float    "base_value"
t.integer  "unit_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false

Spec Fields:

t.string  "label"
t.integer "base_units"

Solution That Seems to Work

I added a "With Spec" scope that uses SQL "IN" with "SELECT"

 def self.with_spec(field_id,value)
    min_value = value.to_f * 0.8
    max_value = value.to_f * 1.2
    where("machines.id IN (SELECT machine_id FROM specs WHERE field_id = ? AND value > ? AND value < ?)",field_id,min_value,max_value)
  end

Upvotes: 1

Views: 1381

Answers (2)

caulfield
caulfield

Reputation: 1373

I think gem meta_search can help you and simplify your code.

Upvotes: 0

Unixmonkey
Unixmonkey

Reputation: 18784

I would build out what I call "filter scopes"; they will reduce the result set if you pass in an hash with approprately named keys. If what is passed in is nil or blank, it ignores that condition.

Then I define a class search method that combines all the filter searches like so:

Class Spec
  belongs_to :machine
  belongs_to :spec_field

  # filter scopes 
  scope :with_machine,  lambda{|*term| where('machine_id = ?',term) if term.present? }
  scope :with_length,   lambda{|*term| where('length = ?',term)     if term.present? }
  scope :with_capacity, lambda{|*term| where('capacity = ?',term)   if term.present? }
  scope :with_width,    lambda{|*term| where('width = ?',term)      if term.present? }

  def self.filter_search(options)
    with_machine(  options[:machine]  ).
    with_length(   options[:length]   ).
    with_capacity( options[:capacity] ).
    with_width(    options[:width]    )
  end

end

Now all you need is to build a form that will have appropriately named inputs:

<%= text_field_tag 'search[machine]', @machine.id %>
<%= text_field_tag 'search[length]' %>
<%= text_field_tag 'search[capacity]' %>
<%= text_field_tag 'search[width]' %>
<%= submit_tag %>

And call it on the controller:

@specs = Spec.filter_search(params[:search]).all

An alternative would be to setup a full-text search engine, and build your search method in much the same way.

Upvotes: 1

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