Collections

  • Prefer map over
    collect.[link]

  • Prefer detect over find. The use of find
    is ambiguous with regard to ActiveRecord’s find method - detect makes
    clear that you’re working with a Ruby collection, not an AR object.
    [link]

  • Prefer reduce over inject.
    [link]

  • Prefer size over either length or count
    for performance reasons.[link]

  • Prefer literal array and hash creation
    notation unless you need to pass parameters to their constructors.
    [link]

    1.   # bad
    2.   arr = Array.new
    3.   hash = Hash.new
    5.   # good
    6.   arr = []
    7.   hash = {}
    9.   # good because constructor requires parameters
    10.   x = Hash.new { |h, k| h[k] = {} }

  • Favor Array#join over Array#* for clarity.
    [link]

    1.   # bad
    2.   %w(one two three) * ', '
    3.   # => 'one, two, three'
    5.   # good
    6.   %w(one two three).join(', ')
    7.   # => 'one, two, three'

  • Use symbols instead of strings as hash keys.
    [link]

    1.   # bad
    2.   hash = { 'one' => 1, 'two' => 2, 'three' => 3 }
    4.   # good
    5.   hash = { :one => 1, :two => 2, :three => 3 }

  • Relatedly, use plain symbols instead of string
    symbols when possible.[link]

    1.   # bad
    2.   :"symbol"
    4.   # good
    5.   :symbol

  • Use Hash#key? instead of
    Hash#has_key? and Hash#value? instead of Hash#has_value?. According
    to Matz, the longer forms are considered deprecated.
    [link]

    1.   # bad
    2.   hash.has_key?(:test)
    3.   hash.has_value?(value)
    5.   # good
    6.   hash.key?(:test)
    7.   hash.value?(value)

  • Use multi-line hashes when it makes the code
    more readable, and use trailing commas to ensure that parameter changes
    don’t cause extraneous diff lines when the logic has not otherwise changed.
    [link]

    1.   hash = {
    2.     :protocol => 'https',
    3.     :only_path => false,
    4.     :controller => :users,
    5.     :action => :set_password,
    6.     :redirect => @redirect_url,
    7.     :secret => @secret,
    8.   }

  • Use a trailing comma in an Array that
    spans more than 1 line[link]

    1.   # good
    2.   array = [1, 2, 3]
    4.   # good
    5.   array = [
    6.     "car",
    7.     "bear",
    8.     "plane",
    9.     "zoo",
    10.   ]