ruby

Ruby

• Prefer method invocation over instance variables ^link

  Example

  ## Bad
  class MarkRecipe
    def initialize(recipe)
      @recipe = recipe
    end
  
    def run
      @recipe.mark
    end
  end
  
  ## Good
  class MarkRecipe
    def initialize(recipe)
      @recipe = recipe
    end
  
    def run
      recipe.mark
    end
  
    private
  
      attr_reader :recipe
  end
  
  ## Also acceptable
  class Image
    def initialize(placeholder: false)
      @placeholder = placeholder
    end
  
    def render
      if placeholder?
        # ...
      end
    end
  
    private
  
      def placeholder?
        !!@placeholder
      end
  end
  
  ## Also acceptable
  class Pager
    def initialize
      @current_page = 1
    end
  
    def run
      while continue?
        # ...
        go_to_next_page
      end
    end
  
    private
  
      attr_reader :current_page
  
      def go_to_next_page
        @current_page += 1
      end
  end

• Avoid using ternary operator ^link

  Example

  ## Bad
  published? ? published_message : standard_message
  
  ## Good
  if published?
    published_message
  else
    standard_message
  end

• Prefer short, focused methods (aim for 1-liners, longer than 5 is a red flag) ^link

• Avoid method names ending in ! ("bang") without a corresponding bang-less, safe version of the method. ^link

  Example

  ## Bad
  def method!
    # dangerous operation, without any safe version (prima-donna)
  end
  
  ## Good
  def method
    # dangerous operation, without any safe version
  end
  
  ## Good
  def method
    # safe version
    # It’s conventional to define the non-bang method in terms of the bang one, i.e.
    dup.method!
  end
  
  def method!
    # dangerous operation, with a safe version
  end

• Prefer small, focused classes (100+ lines is a red flag) ^link

• Prefer extracting private methods over setting variables inside methods ^link

  Example

  ## Bad
  def method
    var_1 = # ...
    var_2 = # ...
    var_3 = # ...
    var_1 + var_2 + var_3
  end
  
  ## Good
  def method
    var_1 + var_2 + var_3
  end
  
    private
  
    def var_1
      # ...
    end
  
    def var_2
      # ...
    end
  
    def var_3
      # ...
    end

• Prefer $stdin, $stdout, $stderr over STDIN, STDOUT, STDERR ^link

• Avoid lines that end with conditionals (exception is guard clauses) ^link

  Example

  ## Bad
  mark_related_items(:spam) if spam_detected?
  
  ## Good
  if spam_detected?
    mark_related_items(:spam)
  end
  
  ## OK for guard clauses, separate by space
  def approve
    return if approved?
    return if unapprovable?
  
    update(approved: true)
  end

• Describe unexplained strings/numbers using constants ^link

  Example

  ## Bad
  def params
    { gak: "UA-4235" }
  end
  
  ## Good
  def params
    { gak: GOOGLE_ANALYTICS_KEY }
  end
  
  ## OK - string explained by hash key
  def params
    { google_analytics_key: "UA-4235" }
  end

• DRY multiple occurrences of values using constants ^link

  Example

  ## Bad
  class Logger
    def log_params
      { google_analytics_key: "UA-4235" }
    end
  end
  
  class Tracker
    def config
      { google_analytics_key: "UA-4235" }
    end
  end
  
  ## Good
  class Logger
    def log_params
      { google_analytics_key: GoogleAnalytics::KEY }
    end
  end
  
  class Tracker
    def config
      { google_analytics_key: GoogleAnalytics::KEY }
    end
  end

• Separate multiline fetch/query methods from the memoized method ^link

  Example

  ## Bad
  def pizza_recipes
    @_pizza_recipes ||= Recipe.
      published.
      in_current_language.
      where("title LIKE ?", "%pizza%")
  end
  
  ## Good
  def pizza_recipes
    @_pizza_recipes ||= fetch_pizza_recipes
  end
  
  def fetch_pizza_recipes
    Recipe.
      published.
      in_current_language.
      where("title LIKE ?", "%pizza%")
  end

• Avoid unless with boolean operator(s) in the conditional ^link

  Example

  ## Bad
  unless client_id.present? && client_secret.present?
    raise "Missing credentials for OauthApplication #{name}."
  end
  
  ## Good - flip to if
  if client_id.blank? || client_secret.blank?
    raise "Missing credentials for OauthApplication #{name}."
  end
  
  ## Good - extract method
  if missing_credentials?
    raise "Missing credentials for OauthApplication #{name}."
  end
  
  def missing_credentials?
    client_id.blank? || client_secret.blank?
  end

• Prefer a custom error class over a plain raise or raising NotImplementedError in abstract methods. ^link

  Example

  ## Bad
  def feed_class
    raise NotImplementedError
  end
  
  def search_source
    raise "Not implemented yet"
  end
  
  ## Good
  def feed_class
    raise UnimplementedAbstractMethodError.new(self.class.name, __method__)
  end