Class Variables and Methods Lab - No BS. Quitting your Job to Code

This lab has the following problem statement: Define a method that returns a hash of unique genres and the number of songs in each genre.

For example:

genre_count = {"rap" => 3, "rock" => 2, "pop" => 1}

We start with a class variable, @@genres which is an array of genres. This array includes duplicates of genres. For example:

@@genres = ["rap", "rock", "rock", "rap", "rap", "pop"]

At this point you have probably guessed that we will use an enumberable to interate over each element of the @@genres array, in order to extract and count the unique genres.

First let’s write some psuedo code:

def self.genre_count
for #each unique genre
count how many times the genre occurs in @@genres
add key value pair to hash
return the hash

We know that the method must be a class method, as it acts on a class variable and the method is generally related to the entire class, not just a single instance! Now that we have a good start on the code logic in psuedo code, lets turn that into machine code.

my solution:

def self.genre_count
count = 0
new_hash = {}
@@genres.uniq each do |genre|
     count = @@genres.count {|x| x ==genre}
		 new_hash[genre] = count
		 end
	new_hash
end

I count the times the uniq genre occurs by iterating over @@genres.uniq. Then I build a hash key value pair with the unique genre as the key, and the count as the value.

Avi’s solution is a bit different and includes an important syntax pattern that has proved to be the eloquent solution to MANY other labs.

Avi’s Solution:

def self.genre_count
   genre_count = {}
	 @@genres.each do |genre|
	    if genre_count[genre] 
			   genre_count[genre] += 1
			else
			   genre_count[genre] = 1
			end
			
	end
	genre_count
	end

What does the following line mean?

if genre[count]

It seems too open ended and unfinished to be an if statement condition! The syntax is a bit strange but the above line translates to: “If genre_count[genre] exists (aka if genre_count for the key [genre] exists) then complete the following. “

so all together the logic reads:

if genre_count of key "genre" exists
    then increment it's count (the value of the key value pair) by one. 
else (if genre_count of key "genre" is nil, or falsey, aka it doesn't exist)
		then CREATE the value/key pair for that genre and set it to one.
		

This is a common pattern which extremely simplified looks like: ```

	if <thing>       //if thing exists
		 do something 
	else                // if it doesn't exist
		 do something else
	```
	
		 Thanks for reading and best of luck with your OO Ruby! 