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http://queirozf.com/reminders/ruby-map-each-collect-inject-reject-select-quick-reference


  • map

    performs an action on each array element. The original array is not modified. Returns the modified array.

    irb> [1,2,3,4,5,6,7,8,9,10].map{|e| e*3}
    => [3, 6, 9, 12, 15, 18, 21, 24, 27, 30]
  • each

    executes an action using as parameter each element of the array. Returns the unmodified array.

    irb> [1,2,3,4,5,6,7,8,9,10].each{|e| print e.to_s+"!"}
    1!2!3!4!5!6!7!8!9!10!
    =>[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  • collect

    synonym for map

  • inject

    takes an accumulator (sum) and changes it as many times as there are elements in the array. Returns the final value of the accumulator.

    irb> [1,2,3,4,5,6,7,8,9,10].inject{|sum,e|sum += e}
    => 55
  • select

    runs an expression for each array element and, if it is true, that element gets added to the output which is returned.

    irb> [1,2,3,4,5,6,7,8,9,10].select{|el| el%2==0}
    => [2,4,6,8,10]
  • reject

    The opposite of select: runs an expression for each array element and includes that element in the output if the expression is false

    irb> [1,2,3,4,5,6,7,8,9,10].reject{|e| e==2 || e==8}
    => [1, 3, 4, 5, 6, 7, 9, 10]



Title
List of Articles
번호 제목 글쓴이 날짜 조회 수
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30 Ruby Style Guide Hojung 2015.02.05 1896
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24 Difference between collect, select, map and each in ruby Hojung 2014.06.10 1476
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19 Optional method parameters in Ruby Hojung 2014.05.29 1665
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