Ruby Basics: Strings, Arrays, & Hashes, oh my! (and cute things)

This is a continuation of Picking up Ruby Fast, as a Python Dev. Again, expect examples with minimal math

Cute Names!!!!

Vicki Langer

@vicki_langer

@yechielk Okay, okay. I think I am liking Ruby. We can have hashrockets and spaceship operators. I'll convert just for them

20:16 PM - 23 Nov 2020

Hashrockets =>

Hashrockets are used in between keys and values in a hash. It's like the : in a python dictionary.

=> # hashrocket

# ruby
pet_age = { 'cheeto' => 5, 'wiley' => '>2 ish', 'puppy' => 12, 'remmy' => 4, 'ruger' => 4 }

# python
pet_age = { 'cheeto' : 5, 'wiley' : '>2 ish', 'puppy' : 12, 'remmy' : 4, 'ruger' : 4 }

Spaceship Operator <=>

The spaceship operator is a tree way comparison. It takes 2 values and compares them with each part of the spaceship then it returns 3 things. The only return values you will get from a <=> are -1, 0, and 1.

Spaceship operator

<=> # spaceship operator

#ruby
cat_age = 12
dog_age = 5

cat_age <=> dog_age

# output
=> -1  # yep, cat is def older than dog

• -1 means <
• 0 means =
• 1 means >

Other than cute names, I don't have too much exciting to report today, just going through the basics to see what methods Ruby uses compared to what Python has for built-in functions. Mostly, it looks like Ruby has chosen better names.

Oh! I did do an exciting thing. I managed to get my way through mapping some hashes together to make lists of popular movies in different categories

Just Some Notes

A bunch of examples for future reference.

Strings and Some Methods

.prepend

add something to the beginning of something else

command = ", leave the cat alone!"
command.prepend("Wiley")

# output
=> "Wiley, leave the cat alone!"

.delete

remove specific characters from strings

string = "Please hire me. I'm excited to learn"
string.delete "aeiou" # removing vowels

# output
=> "pls hr m. I'm xctd t lrn"

Arrays

Ruby uses zero-based indexing, just like Python. Arrays are basically the same as Python lists. The array methods from the Ruby docs seem to basically be the same as the built-functions python has.

.delete

remove specific values from arrays

feels = ["joyful", "irritable", "ecstatic"]
feels.delete "irritable" "mad" # removing negative words

# output
=> ["joyful", "ecstatic"]

though, it seems .reject or .select.with_index would be a better way to remove these. Though, I don't see what's wrong with .delete

feels = ["joyful", "irritable", "ecstatic"]
feels.reject { |word| word == "irritable" || word == "mad"}

# output
=> ["joyful", "ecstatic"]

.map vs .each

I was told the other day that whenever I see .each I should probably use .map. Today, I've learned why. .map collects results and .each does not.

.map is meat to change or transform data.

# .each returns the unchanged object
pets = ["cat", "dog", "fish"]

pets.each { |pet| pet * 2 }

# output
=> ["cat", "dog", "fish"]

# .map returns the changed object
pets = ["cat", "dog", "fish"]

pets.map { |pet| pet * 2 }

# output
=> ["catcat", "dogdog", "fishfish"]

By the way, I've use blocks several times, but I don't think I've talked about what they do and why they are used. Blocks are the code in the curly braces after a method. In the example above, that's { |pet| pet * 2 }. Blocks are used to show how we want the data to change.

Hashes and Some Methods

dictionary == hash

invert

swap keys and values

pet_age = { :cheeto => 5, :wiley => '>2 ish', :puppy => 12, :remmy => 4, :ruger => 4 }
pet_age[:chip] = 0.5 #adds to hash

pet_age.invert

# output
=> {5=>:cheeto, ">2 ish"=>:wiley, 12=>:puppy, 4=>:ruger, 0.5=>:chip}

A bigger .map example

ratings = {
  :g => 'Little Ones',
  :pg => 'Family Time',
  :pg13 => 'Older Kids',
}
dictionary = {
  :g => { :one => 'ratatouille', :two => 'Wall-e', :three => 'Monsters Inc' },
  :pg => { :one => 'Tangled', :two => 'frozen', :three => 'Finding Dory' },
  :pg13 => { :one => 'Avatar', :two => 'Hamilton', :three => 'mulan' }
}

selected = ratings.select do |key, words|
  key == :g or key == :pg or key == :pg13
end

lines = selected.map do |key, section|
  movies = dictionary[key]
  parts = movies.map { |key, movie| "#{movie.split.map(&:capitalize).join(' ')}" }
  "Popular for #{section}: #{parts.join(", ")}."
end

puts lines.join("\n")


"""
# output
=> Popular for Little Ones: Ratatouille, Wall-e, Monsters Inc.
=> Popular for Family Time: Tangled, Frozen, Finding Dory.
=> Popular for Older Kids: Avatar, Hamilton, Mulan.
"""

In the example above, I had to use .split.map(&:capitalize).join(' ') to make each word in the movie name capital. This cuts the string at the space, capitalizes the parts, then puts them back together.

.capitalize only gets the first word and .titleize would work, but only if using Rails.

If you missed the first post in this series, I've heard it's a good read and there's cats.

Picking up Ruby Fast, as a Python Dev

Vicki Langer ・ Nov 12 '20 ・ 3 min read

#ruby #python #codenewbie