Showing posts with the label rails

What are delegate, delegate method, SimpleDelegator in ruby

 delegate methods in Rails, exposing only necessary methods of containing objects, thereby, making them more easily accessible. class Parent   def initialize     @child =   end end class Child   def initialize     @data = []   end   def insert(data)     @data << data   end   def fetch(key)     @data[key]   end end parent = 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 =   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.insert("imrahul") So this is how dele

unterminated string meets end of file +rails

 This error is because you are trying to instert special symbol in record. User.last.update(password: "!@#$") User.last.update(password: "!@/#$") //it will not throw any errors.

Some important and unknown(least used) ruby methods.

 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

Setup a cron job or scheduler for your rails application using whenever gem.

cd path to your project. gem 'whenever', require: false   add it to your gemfile run bundle install bundle exec wheneverize .   //This will create an initial config/schedule.rb Now create your job call it  from config/schedule.rb whenever --update-crontab   //update crontab crontab -l   //list all cron job set :output, "log/cron.log"    //if you want to set log file for cron job then that this line at the top of config/schedule.rb         in production server:                   after deployment :  bundle exec whenever whenever --update-crontab crontab -l source:

Setup ruby god for rails application || Daemons setup for rails application

 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 = {}) do |w|          command        = "bundle exec ruby lib/daemons/#{op

lambda proc and block in rails

this all things basically we used in block level coding and for some custom queries in rails model class Main   [ 1 , 2 , 3 ].each do | num |     puts num   end end def block_method   yield end block_method { puts "Test"} def arg_method   yield   yield 1 end arg_method { |i| puts i*1 rescue nil} # explicit block def explicit_block(&block) #same as yield end explicit_block {puts "This is explicit block"} # lambda lambda_test = -> {puts "This is lambda"} lambda_test.() lambda_test[] # lambda with args arg_lambda = -> (i){ puts i}"test") my_proc = { |x| puts x } # Should work my_lambda = -> { return 1 } puts "Lambda result: #{}" # Should raise exception my_proc = { return 1 } puts "Proc result: #{}" def call_proc   puts "Before proc"   my_proc = Proc.n

unable to install ruby 2.2 in ubuntu 18.04

Try with this commands 1) Install rvm following instructions for Ubuntu on 2) rvm install ruby 2.2.10 3) rvm install ruby 2.2.10 --with-gcc=gcc if its not work then try with this  1. sudo apt purge libssl-dev && sudo apt install libssl1.0-dev 2. rvm install 2.3.5 --autolibs=disable

rails redirect after login devise

devise_scope :user do  authenticated :user do    root 'dashboard#index', as: :authenticated_root  end  unauthenticated do    root 'home#index', as: :unauthenticated_root  end end

Data Scrapping in rails

go to your terminal create a directory mkdir ruby_data_scrapping create directory mkdir lib cd lib/ touch scraper.rb gem install nokogiri  // install gems in local gem install httparty gem install byebug Write code in your scraper.rb require "httparty" require "nokogiri" require "byebug" class Scraper   attr_accessor :parse_page   def initialize       doc = HTTParty.get("")       @parse_page ||= Nokogiri::HTML(doc)   end   def get_prices      item_container.first(2){|x| x.text}   end   private     def item_container        parse_page.css(".tv-data-table__tbody").first.css(".tv-screener-table__result-row").css(".tv-screener-table__cell")     end   prices =   (0...prices.size).each do |index|       puts "Price: #{prices[index]}"   end end now run this scraper ruby scraper.rb

rails scope with argument or dynamic value and join tables

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(' ? ', #{role} ) } //it will work in all versions of rails validate  :validate_mimimum_amount, unless: -> (order) { order.ord_type=='market' || order.ord_type=='manual' }

some minor things in rails

For Date format  .utc.strftime('%d-%m-%Y %H:%M:%S') Alternative to html_safe (raw("<strong class='text-danger'>Decline</strong")). select tag for form_for  <%=, options_for_select({|x|}, f.object.payment_currency), {include_blank: "Select Currency"}, { :class => 'form-control', required: true }) %> zip -r folder_name

Convert numbers in rails like binary to decimal

value.to_i(from).to_s(to) i.e "1000".to_i(2).to_s(10) //here we are converting binary to decimal

decimal to binary converter in rails

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

Authentication via JWT in rails api's

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] 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

best way to compile your assets in rails

rake assets:precompile tmp:clear

Write simple html text in into rails tags

You can write simple text inside rails tag like link_to button_tag, submit_tag, text_field_tag etc.. (raw("<strong class='text-danger'>Decline</strong")) example : <%= link_to  (raw("<strong class='text-danger'>Decline</strong")), welcome_path %>

how to make separate routes for different user in rails

how to make separate routes for different user in rails  Make another routes file in your config folder           config/routes/admin.rb   //i made new file routes/admin.rb inside config folder Now inside your config/routes.rb file paste this           class ActionDispatch::Routing::Mapper             def draw(routes_name)              instance_eval("config/routes/#{routes_name}.rb")))             end           end        // paste this code above this Rails.application.routes.draw line now side your main route file(config/routes.rb) make new routes for admin file like draw :admin Now config/routes.rb will be look like this Rails.application.routes.draw do   draw :admin end Now you can make routes for admin or admin dashboard separately inside your config/routes/admin.rb file resources :admin

ActiveRecord::Base.connection.execute, robust record execute in rails

ActiveRecord::Base.transaction do          ActiveRecord::Base.connection.execute("UPDATE deposits SET amount = #{params[:adjust_amount].to_f} WHERE type = '#{@deposit.type}' AND id = #{} AND currency_id = '#{@deposit.currency_id}'").as_json if params[:adjust_amount].present?          ## update comment          if params[:mt5_history_id].present?            mt5_withdraw_history = Mt5History.find_by_id(params[:mt5_history_id])            mt5_withdraw_history.update(comment: params[:comment])          end        end This do loop will run until all parameter will execute if any record updatation is failed due to some reason all previous record update will be rollback!   

Wicked-PDF not showing images, 'wicked_pdf_image_tag' undefined

Wicked-PDF not showing images, 'wicked_pdf_image_tag' undefined <div>   <%= wicked_pdf_image_tag 'logo.jpg' %> </div> def save   pdf =                         render_to_string(                           template: 'example/pdf_view.pdf.erb',                           layout: 'layouts/application.pdf.erb'))   send_data(pdf,             filename: 'file_name.pdf',             type: 'application/pdf',             disposition: 'attachment')  end 

Download pdf by ajax or javascript or angular js

Click on button for generate pdf  $("#print_selected_label").on("click", function(){    data = []    $("input:checkbox.print_label:checked").each(function(){      data.push($(this).attr("id"));    });   //getting all information of checked checkbox    if(data.length > 0){    // if data is not null       In angular js controller         // var redirect_new = "/admin/v2/orders/print_multiple_label.pdf?" + jQuery.param(data);        // var pdf =, 'Map PDF', '');      By Creating a link by javascript       // var mydiv = document.getElementById("download_pdf");      // var aTag = document.createElement('a');      // var link = " admin/v2/orders/print_multiple_label.pdf?id="+data ;      // aTag.setAttribute('href',link);      // aTag.innerHTML = "link text";      // mydiv.appendChild(aTag);      //; By making http request