Ruby Programming Language :: Corruption when modifying array element


	Corruption when modifying array element When modifying an element in a row, the result becomes corrupted when I try to read it back. new_row is being modified correctly. It is then being appended to new_rows (plural). But when I read new_rows back, each element contains only the last new_row created. What gives? $ cat test.rb;./test.rb #!/usr/bin/env ruby def test1 row = [ 'field1' , 'field2', 'field3' ] test = [ 'test1', 'test2', 'test3' ] new_rows = Array.new new_row = row test.each { \|value\| new_row[2] = value puts "new_row: #{new_row}" new_rows << new_row } puts for ixt in 0..new_rows.size - 1 puts "new_rows[#{ixt}]: #{new_rows[ixt]}" end end test1 new_row: field1field2test1 new_row: field1field2test2 new_row: field1field2test3 new_rows[0]: field1field2test3 new_rows[1]: field1field2test3 new_rows[2]: field1field2test3 -- Posted via http://www.ruby-forum.com/. On May 30, 9:34 pm, Alan Lake <alan.l@lakeinfoworks.com> wrote: > When modifying an element in a row, the result becomes corrupted > def test1 > row = [ 'field1' , 'field2', 'field3' ] > test = [ 'test1', 'test2', 'test3' ] > new_rows = Array.new > new_row = row At this point, new_row is the same object as row -- it is basically a reference to the Array object you created on the first line of test1. > test.each { \|value\| > new_row[2] = value > puts "new_row: #{new_row}" > new_rows << new_row Everytime you do this, you are putting a reference to (new_)row into your new array. All three references refer to the same Array object, which you created on the first line. If you need to do something like this, you can use Array's clone method to create a copy of the array. It will be a new object: arr1 = [1, 2, 3] arr2 = arr1 arr3 = arr1.clone puts arr1.object_id => 24377410 puts arr2.object_id => 24377410 puts arr3.object_id => 24324410 So, try: def test1 row = [ 'field1' , 'field2', 'field3' ] test = [ 'test1', 'test2', 'test3' ] new_rows = [] test.each { \|value\| new_row = row.clone new_row[2] = value puts "new_row: #{new_row}" new_rows << new_row } new_rows.each_with_index do \|v, i\| puts "new_rows[#{i}]: #{new_rows[i]}" end end