why-ruby-classes-are-cool.md

Why classes are cooool!!11

• In my app I have a lot of objects that represent an album.
• Until recently, I was using a generic hash for what I needed
• eg.

album = {
  album_name: "Pure Heroine (Deluxe)",
  artist_name: "Lorde",
  url: "https://music.apple.com/gb/album/pure-heroine/1440818584?uo=4&at%0D=1010lxMt%0D",
  tracks: 10,
  price: 990,
  cover: "https://is5-ssl.mzstatic.com/image/thumb/Music128/v4/17/3c/b3/173cb326-63d7-3936-6302-33848d5caecd/source/200x200bb.jpg",
  id: 1440818584,
  site: :itunes
}

• This worked for me fine
• If I need to get a value, I would just grab it from the hash in the normal way

album_name = album[:album_name]
# >> Pure Heroine (Deluxe)

• If I needed to do something to the album
• like extract 'Deluxe' from the album_name and set a flag
• I would create a method

def normalize(album)
  if album[:album_name].end_with?(" (Deluxe)")
    # update album_name to be name without " (Deluxe)"
    # set new k/v of album[:deluxe] = true
  end
  return album
end

normalized_album = normalize(album)
normalized_album[:album_name]
# >> Pure Heroine
normlized_album[:deluxe]
# >> true

• Often I'd need to grab the artist name and album to use as a search phrase

search_keywords = "#{album[:artist_name]} #{album[:album_name]}"
# >> "Lorde Pure Heroine"

• Doing this is perfectly fine
• But sometimes I would create an album using the wrong key value
• eg. 'album:' instead of 'album_name'
• This would break the methods eg. normalize
• Also, it started to become annoying to keep wrapping the album hash in methods that you had to put in front of it ie. normalize(album)
• I started thinking if there was a better way
• ideally, you want to take the album and then do something to it. Maybe... album.normalize
• So I created an Album class
• This standardises what value types the object can have ie. will error imediately if I try and create using 'album' instead of 'album_name'

class Album
  include ActiveModel::Model

  attr_accessor :release_name, :artist_name, :url, :site, :tracks, :price, :deluxe, :explicitness, :cover, :id, :artist_id
  def initialize(release_name, artist_name, url, site)
    @release_name = release_name
    @artist_name = artist_name
    @url = url
    @site = site
  end
end

album = Album.new("Pure Heroine (Deluxe)", "Lorde", "https://music.apple.com/gb/album/pure-heroine/1440818584?uo=4&at%0D=1010lxMt%0D", :itunes)

• Now you can reference the values you want using a '.'
• A bit nicer than the has approach, but not that different

album.release_name # >> Pure Heroine (Deluxe)
album.artist_name # >> Lorde
album.url # >> https://music.apple.com/gb/album/pure-heroine/1440818584?uo=4&at%0D=1010lxMt%0D
album.site # >> :itunes

• The real benefit comes with the methods that I can include in the class
• eg

class Album
  include ActiveModel::Model

  attr_accessor :release_name, :artist_name, :url, :site, :tracks, :price, :deluxe, :explicitness, :cover, :id, :artist_id
  def initialize(release_name, artist_name, url, site)
    @release_name = release_name
    @artist_name = artist_name
    @url = url
    @site = site
  end

  def normalize
    if self.album_name.end_with?(" (Deluxe)")
      # update album_name to be name without " (Deluxe)"
      # set new k/v of album[:deluxe] = true
    end
    return album
  end


  def artist_release_keywords
    "#{self.artist_name} #{self.album_name}"
  end

  private
    # add methods here that the other methods above might use
    # keeps the main methods clean and readable
    # while keeping all relevant stuff together
end

album.normalize
# >> 
# album_name: "Pure Heroine"
# artist_name: "Lorde"
# url: "https://music.apple.com/gb/album/pure-heroine/1440818584?uo=4&at%0D=1010lxMt%0D"
# site: :itunes
# deluxe: true

album.artist_release_keywords # >> Lorde Pure Heroine

• You can also now easily add validation
• eg. ensure that 'tracks' is an integer
• Because I scrape some results from html, they return as String and I usually forget to convert them which produces errors in other code I use
• You could detect errors early with class validation
• (I haven't actually explored this yet)