IvikGH

# Sort by frequency  
def frequency(arr)
  arr.each_with_object(Hash.new(0)) { |letter, result| result[letter] += 1 }
     .sort_by { |_k, v| -v }.to_h.keys
end

# Flatten a list  
def flatten(arr)
  arr.flatten!
end

IvikGH

# get all students last_name, alphabetically ordered, not repeating
SELECT DISTINCT last_name
FROM   students
ORDER  BY last_name

# get the count of all students in each groups, order by groups names descending
SELECT groups.name,
       Count(students.id)
FROM   groups
       LEFT JOIN students

IvikGH

Transactions

As your business logic gets complex you may need to implement transactions. The classic example is a bank funds transfer from account A to account B. If the withdrawal from account A fails then the deposit to account B should either never take place or be rolled back.

Basics

All the complexity is handled by ActiveRecord::Transactions. Any model class or instance has a method named .transaction. When called and passed a block, that block will be executed inside a database transaction. If there's an exception raised, the transaction will automatically be rolled back.

Example

IvikGH

    let(:inst_client) { double(user: inst_user) }

    let(:inst_user) do
      # instance_double(Instagram::Client, id:           instagram_id,
      double(id:           instagram_id,
                                 access_token: access_token,
                                 username:     name,
                                 full_name:    'John Doe',
                                 picture:      picture)
    end

IvikGH

    let(:instagram_id) { '1234567890' }
    let(:picture) { 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png' }

    let(:inst_client) { double(user: inst_user) }

    let(:inst_user) do
      # instance_double(Instagram::Client, id:           instagram_id,
      double(id:           instagram_id,
                                 access_token: access_token,
                                 username:     name,

IvikGH

$ git remote add staging https://git.heroku.com/staging-app.git
$ git remote add heroku https://git.heroku.com/app.git

IvikGH

.nil? can be used on any object and is true if the object is nil.

.empty? can be used on strings, arrays and hashes and returns true if:

• String length == 0
• Array length == 0
• Hash length == 0

Running .empty? on something that is nil will throw a NoMethodError.

IvikGH

Чтобы не быть голословным:
require 'redis'
require 'connection_pool'

module Shared
  class RedisPool
    DEFAULT_POOL_SIZE = 100.freeze # Per 1 process

    # Closes all the connections and clears the pool
    #

IvikGH

          <div class="switch">
            <input type="checkbox" id="autopayments" class="switch-checkbox" checked="checked">
            <label class="switch-label" for="autopayments">
              <span class="switch-inner"></span>
              <span class="switch-btn"></span>
            </label>
          </div>

IvikGH

ENV["RAILS_ENV"] ||= 'test'
require 'spec_helper'
require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'
require 'devise'
require 'paper_trail/frameworks/rspec'
require "pundit/rspec"

Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }