newbie: defined?(Rails)

rubyonrails-talk
1

hi,

i see the line

if defined?(Rails)

more and more in gems and other require statements. right now im looking at a gem and the line
if defined?(Rails)

is being called prior the first constructor of a class. this seems to be kinda related to autoload rails things, but im not sure.
what is it? if someone could shed some light on it. thx
2

It's checking whether Rails is defined. Typically you might do this if your gem/plugin had some rails features that you don't want to load (or can't be loaded) if your gem is being used in a non Rails context

Fred

3

ok, that makes sense. but where is that variable being ‘declared’ and or set? tia

4

ok, that makes sense. but where is that variable being 'declared' and or set?

Somewhere early in the Rails initialization process (There's probably a module called Rails - as soon as the file containing it is loaded it will spring into existence)

Fred

5

ok, thx for ur insight appreciate it