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After a dedicated 4 weeks of an eat, sleep, and code routine here at this amazing Flatiron program, I arrived at a milestone, my first CLI project. Henceforth, the birth of the Sneaker Finder Ruby Gem. I want to take some time to document my findings. I also want to share the key take away points in my learning journey thus far. I believe this gem summarizes it well. Let’s begin…

What does it do?

How do we use it?

doc = Nokogiri::HTML(open(

The value of the doc variable is the entire web page's HTML. We can call #css on doc which allows us to specify which data on the web page we would like to isolate by using HTML tags, CSS classes, and/or id's as arguments. Once we do this we are set to iterate.

doc.css(".ProductList li")

One thing I wanted to emphasize is how important it is to know the return values for iterators. Much time can be saved when we are aware of this. We can illustrate this well with #map vs #each. In developing this gem I used both of these iterators.

  • #map can be used to modify data, and it always returns this data in an array. Note the following method from the scraper class.
def self.scrape_brand_index_page_one(index_url) 
doc = Nokogiri::HTML(open(index_url))
doc.css(".ProductList li").map do |shoe|
hash = {}
hash[:shoe_name] = shoe.css(".ProductDetails a").first.text
hash[:price] = shoe.css(".ProductPriceRating em").text
hash[:shoe_href] = shoe.css(".ProductDetails a").first['href']

In the CLI, when the user requests to see a collection of shoes, this method would iterate with #map to find the data, assign it to a new hash upon every iteration, and (here is the point) return each hash as an element into a newly created array. Each of these hashes in this array is used to instantiate shoe objects with unique attributes. The #map method is quite useful indeed.

  • #each can be used to modify data within the method but the return value specific to #each will return the same class of object it was called on in an unmodified state.

#each is quite useful when you only want to puts some data. With this gem, I did find another use for it that was a pleasant surprise.

A key objective of this gem is to only scrape the necessary data. Only to look for information if it is requested. Therefore when a user would like to see more information on a single and specific shoe, it is necessary to scrape this data, update what we know on this shoe, and then display this data. So instead of retrieving information for a collection of shoes, we are retrieving information for a single shoe. Programmatically, speaking instead of an array of hashes, we are working with a single hash.

In the below example we see that #each is used to simply modify the content of our hash and the # self.shoe_details then returns this hash.

def self.shoe_details(index_url)
details = Nokogiri::HTML(open(index_url))
hash = {}
details.css(".ProductDetailsGrid").each do |detail|
hash[:shoe_name] = details.css("h1").text
hash[:brand] = details.css(".specs span")[0].text
hash[:condition] = details.css(".specs span")[1].text
hash[:colorway] = details.css(".specs span")[2].text
hash[:year] = details.css(".specs span")[3].text
hash[:productid] = details.css(".specs span")[4].text
hash[:sizes_available] = details.css(".list-horizontal .name").map { |sizes| sizes.text }.join(', ')

Final Words

I would also like to make a shout out to the #send method which greatly simplifies the instantiation of class instances. Below we can see a common set up for this:

def initialize(hash)
hash.each do |key, value|
send("#{key}=", value)
@@all << self

There is really a wealth of knowledge to be had when starting your own project. It is quite encouraging and invigorating to create something out of nothing, so to speak. I am quite happy with the rigorous hours used to develop this gem. I hope you enjoyed my findings.

Stay coding my friends =)

Originally published at on May 30, 2020.

Full-Stack Software Engineer and Lifelong Learner