learn-co-students/oo-student-scraper-online-web-pt-090819

Object-Oriented Student Scraper

Objectives

• Build two classes, a class that is responsible for scraping data from a web page and a class that uses that data to instantiate new objects.
• Understand the contents of a third class that is responsible for the command line interface.
• Use meta-programming to instantiate new instances of a class and add attributes to instances of a class.

Overview

In this lab, you'll be scraping your Learn.co student website. You'll use the index page to grab a list of current students and instantiate a series of Student objects. You'll scrape the individual profile pages of each student to add attributes to each individual student.

We've given you a third class, CommandLineInterface that is responsible for generating students using both the Student and Scraper classes. As you go through this lab, take some time to read through the code in the CommandLineInterface class. Try to understand how it works and how it uses the code in our other classes to create students, add attributes to them, and display them to the user via the command-line interface.

We've also given you an executable file in bin/run that you can execute once you get your tests passing to see your code in action!

Before You Begin

For this project, we'll be scraping data from the student profiles website. Sort of. We can't really give you a project with a full test suite and base those tests on the real live Learn.co website on the real live internet. Why? Because websites change! They get new styling or new information, or they break because someone did something wrong. It happens! So, any tests we write would be based on the website at a given point in time. The code you write to pass those tests would assume that you are scraping a website that may have since changed. Your scraper would pass tests but fail to actually scrape the web page if you tried to run your code by sending a real web request to the real website. That would be terrible! Then you couldn't see your code in action or view the page you were writing code to scrape. Just awful.

Don't worry! We've very cleverly solved this problem for the purposes of this project. We've created a mock-up student site, available here as a GitHub Page

This copy is being maintained only for the purposes of this project, so we don't have to worry about things like the styling changing or the code breaking and affecting our scraper code.

Instructions

Run bundle install first.

The Scraper Class

Let's start with the Scraper class in lib/scraper.rb. In this class you are responsible for defining two methods. The #scrape_index_page method is responsible for scraping the index page that lists all of the students and the #scrape_profile_page method is responsible for scraping an individual student's profile page to get further information about that student.

Reminder: Nokogiri will take care of parsing the actual HTML page. Once parsed, we can use Nokogiri's .css method to access specific elements based on their class or id. After reading the instructions below, inspect the website in a browser to find the appropriate CSS classes for elements you need to scrape. For more information, check out Nokogiri's reference materials for additional information

The .scrape_index_page Method

This is a class method that should take in an argument of the URL of the index page. For the purposes of our test the URL will be https://learn-co-curriculum.github.io/student-scraper-test-page/index.html. This method should use Nokogiri and Open-URI to access that page. The return value of this method should be an array of hashes in which each hash represents a single student. The keys of the individual student hashes should be :name, :location and :profile_url.

Here's a look at the desired behavior:

Scraper.scrape_index_page(index_url)
# => [
        {:name => "Abby Smith", :location => "Brooklyn, NY", :profile_url => "students/abby-smith.html"},
        {:name => "Joe Jones", :location => "Paris, France", :profile_url => "students/joe-jonas.html"},
        {:name => "Carlos Rodriguez", :location => "New York, NY", :profile_url => "students/carlos-rodriguez.html"},
        {:name => "Lorenzo Oro", :location => "Los Angeles, CA", :profile_url => "students/lorenzo-oro.html"},
        {:name => "Marisa Royer", :location => "Tampa, FL", :profile_url => "students/marisa-royer.html"}
      ]

Top-Tip: Remember to use the element inspector in your browser's developer tools to examine each element whose value you are trying to scrape. You can also use binding.pry and experiment with different element selectors in your terminal. It takes a lot of trial and error to find the correct selectors for the desired element.

The .scrape_profile_page Method

This is a class method that should take in an argument of a student's profile URL. It should use Nokogiri and Open-URI to access that page. The return value of this method should be a hash in which the key/value pairs describe an individual student. Some students don't have a Twitter or some other social link. Be sure to be able to handle that. Once written, the following code should return a hash containing info from the provided profile_url:

Scraper.scrape_profile_page(profile_url)

And the returned hash should look like the following:

{
  :twitter=>"http://twitter.com/flatironschool",
  :linkedin=>"https://www.linkedin.com/in/flatironschool",
  :github=>"https://github.com/learn-co",
  :blog=>"http://flatironschool.com",
  :profile_quote=>"\"Forget safety. Live where you fear to live. Destroy your reputation. Be notorious.\" - Rumi",
  :bio=> "I'm a school"
}

The only attributes you need to scrape from a student's profile page are the ones listed above: the Twitter URL, LinkedIn URL, GitHub URL, blog URL, profile quote, and bio. The hash you build using those attributes should be formatted like the one in the example above.

Why class methods?

Why are our scraping methods being defined as class methods? Well, we don't need to store any information about the Scraper once it has completed the job of scraping. We simply need to scrape some information and pass that information along to our Student class. So, we don't need to produce instances of Scraper that maintain their own attributes.

The Student Class

We've already given you the attr_accessors that you are required to have for each individual student.

The student class will use the information returned by the above methods from our Scraper class to create students and add attributes to individual students. However, the Student class shouldn't know about the Scraper class. This means that the Student class shouldn't directly interact with the Scraper class––it shouldn't call on the Scraper class in any of its methods or take in the Scraper class itself as an argument. Why is this? We want our program to be as flexible as possible.

We can imagine any number of applications that use a Student model. So we don't want our Student model to be dependent on how it gets information regarding the students it creates. It should simply be ready to take in that information, regardless of its source (be it scraping, a .csv file, or a form on a website).

The #create_from_collection(students_array)

This class method should take in an array of hashes. In fact, we will call Student.create_from_collection with the return value of the Scraper.scrape_index_page method as the argument. The #create_from_collection method should iterate over the array of hashes and create a new individual student using each hash. This brings us to the #initialize method on our Student class.

The #initialize Method

The #initialize method should take in an argument of a hash and use meta-programming to assign the newly created student attributes and values per the key/value pairs of the hash. Use the #send method to achieve this. This method should also add the newly created student to the Student class' @@all array of all students. You'll need to create this class variable and set it equal to an empty array at the top of your class. Push self into the array at the end of the #initialize method.

The #add_student_attributes Method

This instance method should take in a hash whose key/value pairs describe additional attributes of an individual student. In fact, we will be calling student.add_student_attributes with the return value of the Scraper.scrape_profile_page method as the argument.

The #add_student_attributes method should iterate over the given hash and use meta-programming to dynamically assign the student attributes and values per the key/value pairs of the hash. Use the #send method to achieve this.

Important: The return value of this method should be the student itself. Use the self keyword.

The .all Method

This class method should return the contents of the @@all array.

Our Code in Action

Now that you have all your tests passing, you can run our executable file, which relies on our CommandLineInterface class.

We've provided you with all of the code in the CommandLineInterface class. Take a few minutes to read through this class and gain a strong understanding of how it uses the code you wrote in your Scraper and Student classes to make a request to the local files and scrape the students.

Now run the executable file with ruby bin/run. You should see all of the students you scraped and instantiated puts-ed out to the terminal. Great job!

View Student Scraper on Learn.co and start learning to code for free.