Bug #11659
closedStrange behavior setting previously-undefined local variables with a statement modifier
Description
Consider a previously-undefined local variable var1
:
irb(main):001:0> if defined?(var1).nil?; var1 = 'default'; end; var1
=> "default"
Consider previously-undefined local variables var1
and var2
:
irb(main):001:0> var2 = 'default' if defined?(var1).nil?; var2
=> "default"
Consider a previously-undefined local variable var3
:
irb(main):001:0> var3 = 'default' if true; var3
=> "default"
Consider a previously-undefined local variable var4
:
irb(main):001:0> var4 = 'default' if defined?(var4).nil?; var4
=> nil
Oops! Why is var4
nil? Logically, considering the prior examples, it should be 'default'. Or are we missing something?
http://stackoverflow.com/questions/33537059/unless-defined-is-not-working-in-my-code
Updated by Hanmac (Hans Mackowiak) almost 9 years ago
var2 = 'default' if defined?(var1).nil?; var2
because you got a typo for var2, see the var1 inside.
var4 = 'default' if defined?(var4).nil?; var4
the problem there is that var got defined from the parser before the code is run, so when it does check for defined, var4 is already defined
also checkout:
var = "ok" if false; var #=> nil
Updated by mwpastore (Mike Pastore) almost 9 years ago
That's not a typo. :-) I wanted to intentionally compare and contrast between a scenario where the same variable was being checked and set (#2) and a scenario where two different variables are in play (#4).
I understand about the parser now, and in fact found another question/answer on SO that explains it in a similar manner. So it's not a bug, per se. It is kind of a Ruby "WTF", though, and in this humble Rubyist's opinion violates POLA pretty badly.
Updated by jeremyevans0 (Jeremy Evans) about 5 years ago
- Status changed from Open to Rejected