Ruby on Rails search with multiple parameters

Question

For example in my Car model i have such fields:

color, price, year

and in form partial i generate form with all this fields. But how to code such logic:

user could enter color and year and i must find with this conditions, user could enter just year or all fields in same time...

And how to write where condition? I could write something like:

if params[:color].present?
car = Car.where(color: params[:color])
end

if params[:color].present? && params[:year].present?
car = Car.where(color: params[:color], year: params[:year])
end
and so over....

But this is very ugly solution, i'm new to rails, and want to know: how is better to solve my problem?

Answer 1

Check out the has_scope gem: https://github.com/plataformatec/has_scope

It really simplifies a lot of this:

class Graduation < ActiveRecord::Base
  scope :featured, -> { where(:featured => true) }
  scope :by_degree, -> degree { where(:degree => degree) }
  scope :by_period, -> started_at, ended_at { where("started_at = ? AND ended_at = ?", started_at, ended_at) }
end

class GraduationsController < ApplicationController
  has_scope :featured, :type => :boolean
  has_scope :by_degree
  has_scope :by_period, :using => [:started_at, :ended_at], :type => :hash

  def index
    @graduations = apply_scopes(Graduation).all
  end
end

Thats it from the controller side

Answer 2

I would turn those into scopes on your Car model:

scope :by_color, lambda { |color| where(:color => color)}
scope :by_year, lambda { |year| where(:year => year)}

and in your controller you would just conditionally chain them like this:

def index
  @cars = Car.all

  @cars = @cars.by_color(params[:color]) if params[:color].present?
  @cars = @cars.by_year(params[:year]) if params[:year].present?
end

Answer 3

user_params = [:color, :year, :price]

cars = self
user_params.each do |p|
    cars = cars.where(p: params[p]) if params[p].present?
end

Answer 4

The typical (naive, but simple) way I would do this is with a generic search method in my model, eg.

class Car < ActiveRecord::Base
  # Just pass params directly in
  def self.search(params)
    # By default we return all cars
    cars = all

    if params[:color].present?
      cars = cars.where(color: params[:color])
    end

    if params[:price1].present? && params[:price2].present?
      cars = cars.where('price between ? and ?', params[:price1], params[:price2])
    end

    # insert more fields here

    cars
  end
end

You can easily keep chaining wheres onto the query like this, and Rails will just AND them all together in the SQL. Then you can just call it with Car.search(params).

Answer 5

I think you could use params.permit

my_where_params = params.permit(:color, :price, :year).select {|k,v| v.present?}
car = Car.where(my_where_params)

EDIT: I think this only works in rails 4, not sure what version you're using.

EDIT #2 excerpt from site I linked to:

Using permit won't mind if the permitted attribute is missing

params = ActionController::Parameters.new(username: "john", password: "secret")
params.permit(:username, :password, :foobar)
# => { "username"=>"john", "password"=>"secret"}

as you can see, foobar isn't inside the new hash.

EDIT #3 added select block to where_params as it was pointed out in the comments that empty form fields would trigger an empty element to be created in the params hash.