Common Ruby mistakes in Rails

1. Misuse predicates

	############
	## WRONG ##
	############
	def author?
	if current_user.id == course.user.id
	current_user.add_role(‘author’)
	end
	end
	def has_any_courses?
	current_user.courses.count
	end
	##############
	## RIGHT ##
	##############
	current_user.add_role(‘author’) if author?
	def author?
	current_user.id == course.user.id
	end
	def has_any_courses?
	current_user.courses.size > 0
	end

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2. Forget to explicitly use “present?”, “blank?”, and “nil?”

	############
	## WRONG ##
	############
	if course
	render '...'
	end
	raise NotAuthorized unless auth_token
	##############
	## RIGHT ##
	##############
	if course.present?
	render '...'
	end
	raise NotAuthorized unless auth_token.present?

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3. Don’t use memorization

	############
	## WRONG ##
	############
	def user
	User.find(params[:id})
	end
	user.articles
	user.courses
	##############
	## RIGHT ##
	##############
	def user
	@user ||= User.find(params[:id})
	end
	user.articles
	user.courses

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4. Forget that first come symbols, then single quotes, and then double quotes

	############
	## WRONG ##
	############
	render ‘new’
	social_network = “facebook”
	message = “Can’t do this”
	##############
	## RIGHT ##
	##############
	render :new
	social_network = ‘facebook’
	message = “Can’t do this”

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5. Use some random numbers and lines

	############
	## WRONG ##
	############
	@courses = Course.recent.page(params[:page]).per(3)
	if team.players.count > 13
	# do something
	end
	##############
	## RIGHT ##
	##############
	@courses = Course.recent.page(params[:page]).per(params[:per_page] || PER_PAGE)
	if team.players.count > MAXIMUM_NUMBER_OF_PLAYERS
	# do something
	end

view raw 05-ruby-mistakes.rb hosted with ❤ by GitHub
6. Often choose short or confusing words to name constants

	############
	## WRONG ##
	############
	u = User.last
	CUS_NUM = 100
	##############
	## RIGHT ##
	##############
	last_user = User.last
	CUSTOMERS_NUMBER = 100
	# But:
	form_for @article do |f|
	= f.text_field :title
	create_table :articles do |t|
	t.integer :course_id
	view raw

view raw 06-ruby-mistakes.rb hosted with ❤ by GitHub
7. Excessively use postconditions

	############
	## WRONG ##
	############
	def some_method
	SomeLongClassName.new(params).perform_action if something_true?
	# a lot of another code
	end
	def create
	redirect_to(root_path) if @resource.save
	end
	##############
	## RIGHT ##
	##############
	def some_method
	if something_true?
	SomeLongClassName.new(params).perform_action
	end
	# a lot of another code
	end
	def create
	if @resource.save
	redirect_to root_path
	end
	end

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8. Forget to remove unused parameters and variables, and other unused code

	############
	## WRONG ##
	############
	def find_user( first_name, last_name, date_of birth )
	User.find_by(first_name: first_name)
	end
	##############
	## RIGHT ##
	##############
	def find_user(first_name)
	User.find_by(first_name: first_name)
	end
	view raw

view raw 08-ruby-mistakes.rb hosted with ❤ by GitHub
9. Don’t use “public_send”
Invokes the method identified by symbol, passing it any arguments specified. Unlike send, #public_send calls public methods only. When the method is identified by a string, the string is converted to a symbol.
10. Write long and illegible conditions

	############
	## WRONG ##
	############
	if course.courses_users.where(ban: true).exists?(user_id: id)
	if course.user_id == id
	if #something course.part.exists?(self)
	end
	end
	end
	##############
	## RIGHT ##
	##############
	if part_in?(course) && banned?(course) && author?(course)
	# do something
	end
	def part_in?(course)
	course.part.exists?(self)
	end
	def banned?(course)
	course.courses_users.where(ban: true).exists?(user_id: id)
	end
	def author?(course)
	course.user_id == id
	end

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11. Think less code is always better

	############
	## WRONG ##
	############
	def some_filter
	return unless user_signed_in? || !(current_user.customer? || current_user.admin?)
	redirect_to root_path
	end
	##############
	## RIGHT ##
	##############
	def some_filter
	return unless user_signed_in?
	return if current_user.customer? || current_user.admin?
	redirect_to root_path
	end

view raw 10-ruby-mistakes.rb hosted with ❤ by GitHub
12. Use obsolete syntax

	############
	## WRONG ##
	############
	a = { :bad_code => ‘Some smell’ }
	##############
	## RIGHT ##
	##############
	a = { good_code: ‘No smells’ }

view raw 11-ruby-mistakes.rb hosted with ❤ by GitHub
13. Excessively use “when” and “if”

	############
	## WRONG ##
	############
	def somethod(name)
	case name
	when ‘a’
	‘A’
	when ‘b’
	‘B’
	when '…'
	'...'
	end
	end
	##############
	## RIGHT ##
	##############
	CASES = {
	‘a’ => ‘A’,
	‘b’ => ‘B’,
	}
	def somethod(name)
	CASES[name]
	end
	# or you could go with this option:
	def somethod(name)
	send(:”process_#{name}”)
	end
	def process_a
	‘A’
	end
	def process_b
	‘B’
	end

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14. Don’t use rubocop and other tools for code analysis
Rubocop notice almost all the errors described here
15. Don’t fully understand the point about commenting
Ruby is considered a very high-level language that doesn’t need commenting. Instead of writing another comment to your code, try making it more readable.

https://jetruby.com/