Ruby Method of the Day - Array.reject!

Posted by Kelly McCauley on Nov 21, 2007

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array.reject! {|element| block}  #=> array or nil

array.reject {|element| block} does the exact same thing as Array.delete_if except that it returns nil if no changes were made to array.

Examples

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a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

b = a.clone                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b.reject! {true}            #=> []
b                           #=> []

b = a.clone                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b.reject! {false}           #=> nil
b                           #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

b = a.clone                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b.reject! {|n| n == 3}      #=> [1, 2, 4, 5, 6, 7, 8, 9, 10]
b                           #=> [1, 2, 4, 5, 6, 7, 8, 9, 10]

b = a.clone                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b.reject! {|n| n % 2 == 0}  #=> [1, 3, 5, 7, 9]
b                           #=> [1, 3, 5, 7, 9]

Documentation Reference

Ruby version 1.8.6

www.ruby-doc.org : Array.reject!

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