[ ruby-Bugs-10538 ] sub! causing unexpected side effect

Bugs item #10538, was opened at 2007-05-02 19:17
You can respond by visiting: 
http://rubyforge.org/tracker/?func=detail&atid=1698&aid=10538&group_id=426

Category: Core
Group: 1.8.5
Status: Open
Resolution: None
Priority: 3
Submitted By: Carl Graff (cgramona2)
Assigned to: Nobody (None)
Summary: sub! causing unexpected side effect

Initial Comment:
I have a section of code that behaves unexpectedly in my opinion.

First the section of code:
 def adjust_bol_row(bol_row, hist_bol_row, change_disp = true)
    adj_bol_row = bol_row.dup
    adj_bol_row['DISPOSITION'] = 'ADD' if change_disp
    adj_bol_row['SHIPMENT_PRI_REF'].sub!(/-..-/,hist_bol_row['SHIPMENT_PRI_REF'][/-..-/]) if hist_bol_row
    return adj_bol_row
  end

The statement:
    adj_bol_row['SHIPMENT_PRI_REF'].sub!(/-..-/,hist_bol_row['SHIPMENT_PRI_REF'][/-..-/]) if hist_bol_row

Causes adj_bol_row['SHIPMENT_PRI_REF'] to get updated as expected BUT has the side affect of updating bol_row['SHIPMENT_PRI_REF']

When I use this code
 def adjust_bol_row(bol_row, hist_bol_row, change_disp = true)
    adj_bol_row = bol_row.dup
    adj_bol_row['DISPOSITION'] = 'ADD' if change_disp
    adj_bol_row['SHIPMENT_PRI_REF'] =
      adj_bol_row['SHIPMENT_PRI_REF'].sub(/-..-/,hist_bol_row['SHIPMENT_PRI_REF'][/-..-/]) if hist_bol_row
    return adj_bol_row
  end

Only hash element adj_bol_row['SHIPMENT_PRI_REF'] gets updated as I expect.

Why would sub! in this case cause another hash to get updated?

Thanks,
 Carl







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Comment By: Sam Roberts (sam)
Date: 2007-05-02 21:07

Message:
You duplicated the hash, you didn't duplicate the values in the hash. Use .id or .object_id to see this:
ensemble:~ % irb 
irb(main):001:0> s = "hi\n"
=> "hi\n"
irb(main):002:0> h0={4=>s}
=> {4=>"hi\n"}
irb(main):003:0> h1=h0.dup
=> {4=>"hi\n"}
irb(main):005:0> s.id
=> 371264
irb(main):006:0> h0[4].id
=> 371264
irb(main):007:0> h1[4].id
=> 371264
irb(main):008:0> 

Its the same string.

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