Fetching array of data from DB using Rails 3

Question

I want to access multiple columns using Rails 3.But it gave me the following error.

Error:

ArgumentError (wrong number of arguments (2 for 1)):
  app/controllers/payments_controller.rb:13:in `check_type'

Check my below code.

payment_controller.rb:

class PaymentsController < ApplicationController

    def payment
        @payment=Vendor.new
        respond_to do |format|
            format.html 
            format.js
        end

    end
    def check_type  
        if params[:commit]=="submit"
           @vendor_type=PaymentVendor.where(:v_name => params[:v_name]).pluck(:type ,:Receipt_No)
           @vendor_type.each do |vendor|

            end
        else
            @v_name=Vendor.where(:s_catagory => params[:payment][:s_catagory] ).pluck(:v_name)
        end
    end
end

Actually i want to retrive data like below format.

@vendor_type=["Receipt_no":"type","Receipt_no":"type",.....]

Once these data will appear,I need how to access row values according to Receipt_No.Please help me to resolve this error.

Gagan Gami · Accepted Answer · 2015-04-28 08:55:34Z

3

Thanks to ActiveRecord >= 4 . pluck accepts multiple arguments so in

Rails 4: Your query will work

@vendor_type=PaymentVendor.where(:v_name => params[:v_name]).pluck(:type ,:Receipt_No)

Now as you are using Rails 3 which doesn't support multiple arguments to pluck then we can extend ActiveRecord::Relation itself like this:

put your file under config/initializers

# pluck_all.rb
module ActiveRecord
  class Relation
    def pluck_all(*args)
      args.map! do |column_name|
        if column_name.is_a?(Symbol) && column_names.include?(column_name.to_s)
          "#{connection.quote_table_name(table_name)}.#{connection.quote_column_name(column_name)}"
        else
          column_name.to_s
        end
      end

      relation = clone
      relation.select_values = args
      klass.connection.select_all(relation.arel).map! do |attributes|
        initialized_attributes = klass.initialize_attributes(attributes)
        attributes.each do |key, attribute|
          attributes[key] = klass.type_cast_attribute(key, initialized_attributes)
        end
      end
    end
  end
end

Now in your controller you can pass multiple arguments to pluck like this:

# payment_controller.rb:
@vendor_type=PaymentVendor.where(:v_name => params[:v_name]).pluck_all(:type ,:Receipt_No)

Now you can use pluck_all in whole app. Hope this helps ;)

EDIT: Try below code if plcuk_all not worked:

@vendor_type = PaymentVendor.where(:v_name => params[:v_name]).map{|v|[v.type ,v.Receipt_No]}

Reference for more info: http://meltingice.net/2013/06/11/pluck-multiple-columns-rails/

edited Apr 28, 2015 at 8:55

answered Apr 27, 2015 at 13:46

Gagan Gami

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10 Comments

rajat_474 Over a year ago

@ Gagan: Your answer is always helpful and hope..it will help me a lot.I cannot implement right now..i will update you tomorrow..

rajat_474 Over a year ago

@ Gagan : I did as per you defined but still it is giving me the error as-NoMethodError (undefined method `pluck_all' for #<ActiveRecord::Relation:0x20274 78>):.Please help me to resolve this error..

Gagan Gami Over a year ago

@rajat_474 : I have to checkout with Rails 3. Currently you can use jon snow answer or refer provided link. I will test it myself then will let u update. Till that time you can use other solution.

rajat_474 Over a year ago

Ok...i am trying to use jon's method.

rajat_474 Over a year ago

@ Gagan ,Do you have any other solution for this?

|

jon snow · Accepted Answer · 2015-04-28 08:01:13Z

1

Your pluck(:type ,:Receipt_No) looks wrong, pluck have only one argument.

Also your type of data @vendor_type is wrong, Array don't have key, value pair.

Use map like this,

@vendor_type=PaymentVendor.where(:v_name => params[:v_name]).map { |i| [i.Receipt_No] }

edited Apr 28, 2015 at 8:01

answered Apr 27, 2015 at 13:14

jon snow

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7 Comments

Ian Kenney Over a year ago

pluck support multiple columns from rails 4 but only one in rails 3

rajat_474 Over a year ago

@Ian : So Is there any other way to access multiple column in Rails 3?

jon snow Over a year ago

Array don't have key, value pair. your expected @vendor_type is wrong.

Ian Kenney Over a year ago

you could look at apidock.com/rails/v3.2.3/ActiveRecord/QueryMethods/select

jon snow Over a year ago

use map to get your expected one.

|

Carpela · Accepted Answer · 2016-05-19 12:56:50Z

In terms of making a rails 3 method that behaves the same as the Rails 4 pluck with multiple columns. This outputs a similar array (rather than a hashed key value collection). This should save a bit of pain if you ever come to upgrade and want to clean up the code.

See this tutorial which outlines a similar method that outputs a hash.

config/initializers/pluck_all.rb
module ActiveRecord
  class Relation
    def pluck_all(*args)
      args.map! do |column_name|
        if column_name.is_a?(Symbol) && column_names.include?(column_name.to_s)
          "#{connection.quote_table_name(table_name)}.#{connection.quote_column_name(column_name)}"
        else
          column_name.to_s
        end
      end

      relation = clone
      relation.select_values = args
      klass.connection.select_all(relation.arel).map! do |attributes|
        initialized_attributes = klass.initialize_attributes(attributes)
        attributes.map do |key, attribute|
          klass.type_cast_attribute(key, initialized_attributes)
        end
      end
    end
  end
end

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