Fetching array of data from DB using Rails 3 - ruby

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.

Answer 1

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/

Answer 2

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] }

Answer 3

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
Standing on the shoulders of giants and all