1. Rails Web Scraper Free
2. Open Source Web Scraper
3. Web Scraper Extension Chrome
4. Rails Web Scraper Download

What is Web Scraping?

Web scraping is a technique to extract a large amount of data from a website and display it or store it in a file for further use.

It is used to crawl and extract the required data from a static website or a JS rendered website.

IMDB providing its own api to get the movie details you can use that, this article is a web scraping example. We will get the movie rating, number of rating, name and many more, for this we use BeautifulSoup and Requests packages.

Few terms to get familiar with:

• Nokogiri:
  • Uses CSS selectors or XPath for web scraping.
• Capybara:
  • Allows JS-based interaction with the websites.
• Kimurai:
  • It is a web scraping framework in ruby.
  • Combination of Nokogiri + Capybara.
  • Allows scraping data for JS rendered websites and even static HTTP requests.

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• 2) Octoparse Octoparse is a web scraping tool easy to use for both coders and non-coders and popular for eCommerce data scraping. It can scrape web data at a large scale (up to millions) and store it in structured files like Excel, CSV, JSON for download.

While scraping web data, many people fail to see how their web scraping adversely affects the website and the server. To expedite the processing of scraping the data, your scraper may make too frequent requests and slow down or bring down the server. Search engine scraping is the process of harvesting URLs, descriptions, or other information from search engines such as Google, Bing or Yahoo. This is a specific form of screen scraping or web scraping dedicated to search engines only.

Rails Web Scraper Free

There are few tools available for web scrapings such as Nokogiri, Capybara and Kimurai. But, Kimurai is the most powerful framework to scrape data.

Kimurai

A web scraping framework in ruby works out of the box with Headless Chromium/Firefox, PhantomJS, or simple HTTP requests and allows us to scrape and interact with JavaScript rendered websites.

Features :

• Scrape JS based websites.
• Supports Headless Chrome, Headless Firefox, PhantomJS or Simple HTTP requests(mechanize) engines.
• Capybara methods used to fetch data.
• Rich library for built-in helpers to make scraping easy.
• Parallel Scrapping – Process web pages concurrently.
• Pipelines: To organize and store data in one place for processing all spiders.

You can also scrape data from JS rendered websites, i.e. infinite scrollable websites and even static websites. Amazing right !!!

Read Also: Web scraping using Mechanize in Ruby on Rails

Static Websites:

You can use this framework in 2 ways:

1. Making a rails app and extract information with the help of models and controllers.
   • Create a new rails app.

rails _5.2.3_ new web_scrapping_demo --database=postgresql

• • Change the database configurations in app/config/database.yml as per the requirement to run in the development environment.
  • Open rails console and create a database for the web app:

rails db:create

• • Add gem ‘kimurai’ to Gemfile.
  • Install the dependencies using:

bundle install

• • Generate a model using the below command with the parent as Kimurai::Base instead of ApplicationRecord:

rails g model Web Scrapper --parent Kimurai::Base

• • Perform database migrations for this generated model.

rails db:migrate

• • Generate a controller using:

rails g controller WebScrappersController index

• • Make a root path for the index action:

root 'web_scrappers#new'

• • Add routes for WebScrapper model:

resources: web_scrapper

• • Add a link to the index.html.erb file as shown below:

<%= link_to 'Start Scrap', new_web_scrapper_path %>

• • Now add an action in the WebScrappersController to perform scraping:

def new
Web Scrapper.crawl!
end

Note: Here, crawl! Performs the full run of the spider. parse method is very important and should be present in every spider. The entry point of any spider is parse.

• • Now add some website configurations in the model for which you need to perform scrapping.

Here,

@name = name of the spider/web scraper

@engine = specifies the supported engine

@start_urls = array of start URLs to process one by one inside parse method.

@config = optional, can provide various custom configurations such as user_agent, delay, etc…

Read the Case Study about – Web Scraping RPA (Data Extraction)

Note: You can use several supported engines here, but if we use mechanize no configurations or installations are involved and work for simple HTTP requests but no javascript but if we use other engines such as selenium_chrome, poltergeist_phantomjs, selenium_firefox are all javascript based and rendered in HEADLESS mode.

• • Add the parse method to the model for initiating the scrap process.

Here, in the above parse method,

response = Nokogiri::HTML::Document object for the requested website.

URL = String URL of a processed web page.

data = used to pass data between 2 requests.

The data to be fetched from a website is selected using XPath and structures the data as per the requirement.

• • Open the terminal and run the application using:

rails s

• • Click on the link 'Start Scrap'
    • The results will be saved in the results.json file using save_to helper of the gem.

• • Now, check out the stored JSON file, you will get the scraped data.

Hooray !! You have extracted information from the static website.

• Making a simple ruby file for extracting the information.

1. • Open the terminal and install kimurai using the below-mentioned command:

gem install kimurai

• • You can refer to the code written for the generated model and make a ruby file using it.
  • Run that ruby file using:

ruby filename.rb

Dynamic Websites / JS rendered websites:

Pre-requisites:

Install browsers with web drivers:

For Ubuntu 18.04:

• For automatic installation, use the setup command:

$ kimurai setup localhost --local --ask-sudo

Note: It works using Ansible. If not installed, install using:

$ sudo apt install ansible

• Firstly, install basic tools:

sudo apt install -q -y unzip wget tar openssl
sudo apt install -q -y xvfb

• For manual installation, follow the commands for the specific browsers.

You can use this framework in 2 ways:

• Making a rails app and extract information with the help of models and controllers.
  • Follow all the above steps from a to o for static websites.
  • Change the @engine from :mechanize to :selenium_chrome for using chrome driver for scraping.
  • Also, change the parse method in the model to get the desired output.

• Making a simple ruby file for extracting the information.
  • Open the terminal and install kimurai using the below-mentioned command:

gem install kimurai

• • You can refer to the code written for the generated model in the section of the dynamic website and make a ruby file using it.
  • Run that ruby file using:

ruby filename.rb

You can find the whole source code here.

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A design pattern is a repeatable solution to solve common problems in a software design. When building apps with the Ruby on Rails framework, you will often face such issues, especially when working on big legacy applications where the architecture does not follow good software design principles.

This article is a high-level overview of design patterns that are commonly used in Ruby on Rails applications. I will also mention the advantages and disadvantages of using design patterns as, in some cases, we can harm the architecture instead of making it better.

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An appropriate approach to using design patterns brings a lot of essential benefits to the architecture that we are building, including:

• Faster development process - we can speed up software creation by using tested and well-designed patterns.
• Bug-free solutions - by using design patterns, we can eliminate some issues that are not visible at an early stage of the development but can become more visible in the future. Without design patterns, it can become more challenging to extend the code or handle more scenarios.
• More readable and self-documentable code - by applying specific architecture rules, we can make our code more readable. It will be easier to follow the rules by other developers not involved in the creation process.

Although design patterns were created to simplify and improve the architecture development process, not appropriate usage can harm the architecture and make the process of extending code even harder.

The wrong usage of design patterns can lead to:

• The unneeded layer of logic - we can make the code itself more simple but split it into multiple files and create an additional layer of logic that will make it more challenging to maintain the architecture and understand the rules by someone who is not involved in the creation process since day one.
• Overcomplicated things - sometimes a meaningful comment inside the class is enough, and there is no need to apply any design patterns which only seemingly clarify the logic.

This section of the article covers the most popular design patterns used in Ruby on Rails applications, along with some short usage examples to give you a high-level overview of each pattern’s architecture.

Service

The service object is a very simple concept of a class that is responsible for doing only one thing:

The above class is responsible only for scraping the website title.

Value object

The main idea behind the value object pattern is to create a simple and plain Ruby class that will be responsible for providing methods that return only values:

The above class is responsible for parsing the email’s value and returning the data related to it.

Open Source Web Scraper

Presenter

This design pattern is responsible for isolating more advanced logic that is used inside the Rails’ views:

We should keep the views as simple as possible and avoid putting the business logic inside of them. Presenters are a good solution for code isolation that makes the code more testable and readable.

Decorator

The decorator pattern is similar to the presenter pattern, but instead of adding additional logic, it alters the original class without affecting the original class’s behavior.

We have the Post model that provides a content attribute that contains the post’s content. On the single post page, we would like to render the full content, but on the list, we would like to render just a few words of it:

In the above example, I used the SimpleDelegator class provided by Ruby by default, but you can also use a gem like Draper that offers additional features.

Builder

The builder pattern is often also called an adapter. The pattern’s main purpose is to provide a simple way of returning a given class or instance depending on the case. If you are parsing files to get their contents you can create the following builder:

Now, if you have the file_path, you can access the rows without worrying about selecting a good class that will be able to parse the given format:

Form object

The form object pattern was created to make the ActiveRecord’s models thinner. We can often create a given record in multiple places, and each place has its rules regarding the validation rules, etc.

Let’s assume that we have the User model that consists of the following fields: first_name, last_name, email, and password. When we are creating the user, we would like to validate the presence of all attributes, but when the user wants to sign in, we would like only to validate the presence of email and password:

Thanks to this pattern, we can keep the User model as simple as possible and put only the logic shared across all places in the application.

Policy object

The policy object pattern is useful when you have to check multiple conditions before performing a given action. Let’s assume that we have a bank application, and we would like to check if the user can transfer a given amount of money:

The validation logic is isolated, so the developer who wants to check if the user can perform the bank transfer doesn’t have to know all conditions that have to be met.

Query object

As the name suggests, the class following the query object pattern isolates the logic for querying the database. We can keep the simple queries inside the model, but we can put more complex queries or group of similar queries inside one separated class:

Of course, the query object doesn’t have to implement only class methods; it can also provide instance methods that can be chained when needed.

Observer

The observer pattern was supported by Rails out of the box before version 4, and now it’s available as a gem. It allows performing a given action each time an event is called on a model. If you would like to log information each time the new user is created, you can write the following code:

It is crucial to disable observers when running tests unless you test the observers’ behavior as you can slow down all tests.

Interactor

The interactor pattern is all about interactions. Interaction is a set of actions performed one by one. When one of the actions is stopped, then other actions should not be performed. Interactions are similar to transactions, as the rollback of previous actions is also possible.

To implement the interactor pattern in the Rails application, you can use a great interactor gem. If you are implementing the process of making a bank transfer, you can create the following structure:

Each class represents one interaction and can now be grouped:

We can now perform the whole interaction by calling the organizer along with the context data. When one of the interactors fail, the next interactors won’t be executed, and you will receive a meaningful output:

The interactor pattern is a perfect solution for complex procedures where you would like to have full control over the steps and receive meaningful feedback when one of the procedures fail to execute.

Null object

The null object pattern is as simple as the value object as they are based on plain Ruby objects. The idea behind this pattern is to provide a value for non-existing records.

If in your application the user can set its location, and you want to display information when it’s not set, you can achieve it by using the if condition or creating the NullLocation object:

Inside the User model, you can make usage of it:

Web Scraper Extension Chrome

You can now fetch the full version of the address without worrying about the object persistence:

Rails Web Scraper Download

I haven’t mentioned all the design patterns that are used as there are plenty of them. Some of them are more useful; some are less. Any design pattern should be used with caution. When using them not correctly, we can harm our architecture and overcomplicate the code, which leads to longer development time and higher technical debt.