# \[Backport #1915\] const\_defined?$B$N(B1.9$B$H$N5sF0$N0c$$$K$D$$$F(B

**URL:** <https://www.ruby-forum.com/t/backport-1915-const-defined-b-n-b1-9-b-h-n5sf0-n0c-k-d-f-b/173442>\
**Category:** Development\
**Created:** [August 9, 2009, 1:08am UTC](https://www.ruby-forum.com/t/backport-1915-const-defined-b-n-b1-9-b-h-n5sf0-n0c-k-d-f-b/173442 "2009-08-09T01:08:12Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Akira\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a183cd/32.png) [@Akira\_M](https://www.ruby-forum.com/u/Akira_M)\
**Post date:** [August 9, 2009, 1:08am UTC](https://www.ruby-forum.com/t/backport-1915-const-defined-b-n-b1-9-b-h-n5sf0-n0c-k-d-f-b/173442/1 "2009-08-09T01:08:12Z")

</div>

Backport #1915: const\_defined?e$B$Ne(B1.9e$B$H$N5sF0$N0c$$$K$D$$$Fe(B  
[http://redmine.ruby-lang.org/issues/show/1915](http://redmine.ruby-lang.org/issues/show/1915)

e$B5/I\<\<Te(B: Akira M.  
e$B%9%F!\<%?%9e(B: Open, e$BM%@hEYe(B: Normal  
e$B%+%F%4%je(B: core

e$B0J2\<$N\>l9g$Ke(B  
% cat const\_defined.rb  
class Alpha  
class Beta; end  
end

class Gamma \< Alpha; end

puts Gamma::const\_get(‘Alpha’)

puts Gamma::const\_defined?(‘Alpha’)

1.8e$B$He(B1.9e$B$G$O$=$l$\>$l$3$&$J$j$^$9!#e(B  
% ruby18 -v  
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin9]  
% ruby18 const\_defined.rb  
Alpha  
false  
% ruby19 -v  
ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-darwin9.7.0]  
% ruby19 const\_defined.rb  
Alpha  
true

1.9e$B$+$i;EMM$,JQ99$5$l$?$H$$$&$3$H$J$N$+$J!“$H;W$&$N$G$9$,!”$3$l$Oe(B1.8.xe$B$K%P%C%/%]!\<%H$5$l$kM=Dj$O$"$k$N$G$7$g$&$+!)e(B

---

<div class="post-metadata">

**Author:** ![Akira\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a183cd/32.png) [@Akira\_M](https://www.ruby-forum.com/u/Akira_M)\
**Post date:** [August 14, 2009, 1:47pm UTC](https://www.ruby-forum.com/t/backport-1915-const-defined-b-n-b1-9-b-h-n5sf0-n0c-k-d-f-b/173442/2 "2009-08-14T13:47:34Z")

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e$B%A%1%C%He(B #1915 e$B$,99?7$5$l$^$7$?!#e(B (by Akira M.)

e$B$3$N7o$K4X$7$F!“@hF|$Ne(BAsakusa.rbe$B$G$$$/$D$+H=L@$7$?$3$H$,$”$k$N$GDI5-$7$^$9!#e(B

% cat const.rb  
class Alpha  
class Beta; end  
end

class Gamma \< Alpha  
puts defined?(Beta)  
end

puts Gamma::const\_get(‘Beta’)

puts Gamma::const\_defined?(‘Beta’)  
puts Gamma::Beta

% ruby18 const.rb  
constant  
Alpha::Beta  
false  
Alpha::Beta  
% ruby19 const.rb  
constant  
Alpha::Beta  
true  
Alpha::Beta

e$B$?$@$7!"e(BRuby 1.9e$B$G$O!"e(B  
puts Gamma::const\_defined?(‘Beta’)  
e$B$N$H$3$m$re(B  
puts Gamma::const\_defined?(‘Beta’, false)  
e$B$H=q$1$P!"e(B1.8e$B$HF1MM$Ke(Bfalsee$B$K$J$j$^$9!#e(B

e$B$D$^$j!“LdBj$Oe(B2e$BE@$”$C$F!"e(B

1. Ruby 1.9e$B$Ne(B const\_defined?  
e$B$O0z?t$re(B2e$B$D\<h$l$k$h$&$K3HD%$5$l$F$$$k$,!"$3$NE@$K4X$7$F$Oe(B1.8e$B$K%P%C%/%]!\<%H$5$l$F$$$J$$!#e(B
2. 

## 1.8e$B$N5sF0e(B(defined?e$B$de(Bconst\_gete$B$G8+$($F$k$N$Ke(Bconst\_defined?e$B$G$O8+$($J$$e(B)e$B$,$J$s$@$+L7=b$7$F$$$k$h$&$K8+$($k!#e(B e$B$H$$$&$3$H$+$H;W$o$l$^$9!#e(B

[http://redmine.ruby-lang.org/issues/show/1915](http://redmine.ruby-lang.org/issues/show/1915)