Hypertechblog

 delegate methods in Rails, exposing only necessary methods of containing objects, thereby, making them more easily accessible. class Parent   def initialize     @child = Child.new   end end class Child   def initialize     @data = []   end   def insert(data)     @data << data   end   def fetch(key)     @data[key]   end end parent = Parent.new if you try this parent.insert("imrahul") then you will get response undefined method `insert' for #<Parent:0x000055f4915673a0 @child=#<Child:0x000055f491567350 @data=[]>> (NoMethodError)   This code will work if we overide methods of child class class Parent   def initialize     @child = Child.new   end   def insert(data)     @child.insert(data)   end   def fetch(index)     @child.fetch(index)   end end class Child   def initialize     @data = []   end   def insert(data)     @data << data   end   def fetch(key)     @data[key]   end end parent = Parent.new parent.insert("imrahul") So this is how dele

What is with_lock? how it work Ans:  If two users read a value from a record and then update it simultaneously, one of the values has to “win” and data integrity will be compromised. This is dangerous especially when dealing with money or inventory stocks. For example: User has a card balance = 10 User opens browser A and fill out 5 USD to buy User opens browser B and fill out 10 USD to buy User hits “Buy” button of both browsers at the same time Request A reads card balance=10 Request B reads card balance=10 Request A updates balance -= 5 (balance now is 10-5=5) Request B still has the instance card balance=10 (even though request A already decremented it) Request B updates balance -= 10 (balance now is 10-10=0) Final balance is now 0 User was able to purchase 15 USD when the initial balance was only 10 USD. This is race condition potentially at its worst case! Rails doesn’t do locking when loading a row from the database by default. If the same row of data from a table is loaded by t

  require 'openssl' OpenSSL::SSL::VERIFY_PEER = OpenSSL::SSL::VERIFY_NONE put this lines in config/application.rb

 1) How flash message work in ruby on rails? Ans. They are stored in your session store. The default since rails 2.0 is the cookie store, but check in config/initializers/session_store.rb to check if you're using something other than the default. According to APIdock : ActionController/Flash, it is stored in a session. Note that if sessions are disabled only flash.now will work. When using flash.now, your values are not available in the next request. 2) What is the use of Asset-PipeLine in Rails? Ans. Assets(css, scss, js, coffeescript, images etc), its fast executed in rails application because of asset pipeline when we compile it or when its compiled, it will generate a single source code file or a manifest file, so that's why assets are interpret fastly. 3)   Difference between find and find_by? Ans . The find method is usually used to retrieve a row by ID:            Model.find(1)           And it will throw ActiveRecord::RecordNotFound error if record not found. find_by is

 1) inject or reduce      When called, the inject method will pass each element and accumulate each sequentially.     ex:         [1,2,3].inject(:+)    => ((1+2)+3))   //we have can any operator here i.e +,-,*,/,%         OR         [1,2,3].inject{|sum, value| sum + value } => 1 iteration:  (1 + 2)                                                                                             =>  2 iteration: (3(1st iteration sum)+3)            we  can also pass it a default value or base value for the accumulator.     ex:          [1,2,3].inject(0, :+)    => (0+(1+2)+3)) //so here initial value for sum is 0.          We can also use inject menthods for building hash's from the array's     ex:           [[:book, "data structure"], [:price, "400rs"]].inject({}) do |result, element|               result[element.first] = element.last               result           end            #=> {:book=>"data structure", :price=>"400rs&qu

 1) Install god on Ubuntu/Linux machine      sudo apt update      sudo apt install ruby-god 2) Create new rails application if you don't have existing 3) In your Gemfile add new gem       gem 'god', '~> 0.13.7', require: false 4) Then run bundle install 5) create a folder named daemons inside your  lib folder 6) create a file name daemons.god inside daemons folder (this file name or folder name can be anything its totally up to you) 7) Then paste this on you daemons.god file      ENV["RAILS_ENV"] = "development"      RAILS_ENV  = ENV.fetch('RAILS_ENV', 'production')      RAILS_ROOT = File.expand_path('../../..', __FILE__)      require 'shellwords'      # Create non-default log/daemons directory.      require 'fileutils'      FileUtils.mkdir_p "#{RAILS_ROOT}/log/daemons"      def daemon(name, options = {})        God.watch do |w|          command        = "bundle exec ruby lib/daemons/#{op

scope :get_by_currency, -> (currency) {find_by(currency_id: currency)} scope :by_role, ->(role) { joins(:roles).where(roles: { name: role }) } //it will work in rails 4 and previous version scope :by_role, ->(role) { joins(:roles).where('roles.name ? ', #{role} ) } //it will work in all versions of rails validate  :validate_mimimum_amount, unless: -> (order) { order.ord_type=='market' || order.ord_type=='manual' }

def dec2bin(number)     number = Integer(number) //number that you have to convert     if(number == 0) then 0 end              new_num = ""     while(number != 0)         new_num = String(number % 2) + new_num         number = number / 2     end     new_num // return new number end

gem 'jwt' add this gem to your gem file bundle install create a file in lib/json_web_token.rb and paste following code class JsonWebToken      SECRET_KEY = Rails.application.secrets.secret_key_base. to_s      def self.encode(payload, exp = 15.days.from_now)         payload[:exp] = exp.to_i        JWT.encode(payload, SECRET_KEY)      end     def self.decode(token)        decoded = JWT.decode(token, SECRET_KEY)[0]        HashWithIndifferentAccess.new decoded     end end create another file config/initializers/jwt.rb and paste following code require 'json_web_token' Now inside controller/api/v1/ we will a parent class for our all end-points: api/v1/api_controller.rb class Api::V1::ApiController < ActionController::Base      protect_from_forgery with: :null_session      def autheticate_user         header = request.headers['Authorization']         header = header.split(' ').last if header         begin             @decoded = JsonWebToken.decode