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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
31 Different Ways to Set Attributes in ActiveRecord (attribute, create, update, validation) Hojung 2015.05.24 2036
30 Ruby Style Guide Hojung 2015.02.05 2483
29 Refresh content automatically after some period time on Rails Hojung 2015.01.22 3010
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24 Difference between collect, select, map and each in ruby Hojung 2014.06.10 1858
23 remove nil from array (compact, compact!) Hojung 2014.06.10 2225
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20 Get list of a class' instance methods Hojung 2014.06.01 1967
19 Optional method parameters in Ruby Hojung 2014.05.29 2075
18 Best Ruby On Rails Content Management Systems (CMS) Hojung 2014.04.26 3256
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12 optparse: mandatory and optional arguments example Hojung 2014.03.14 3010
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