Stuck with modules/classes/inheritance

[Kev Jackson]

given:

test.rb :

require 'b'

b = B.new


lib/base.rb:

module A
class Base
end
end

lib/b.rb:

module A
class B < Base
end
end


Why do I get

/lib/b.rb:2: uninitialized constant A::Base (NameError)
from test.rb:1:in `require'
from test.rb:1

?

This is a stripped down version of what I want to do (ie organize my
code into a module, but still keep classes in separate files, have a
base class and inherit).

It's probably something trivial, but at the moment I'm stuck - any help
would be (as always) greatly appreciated

Kev

 

[Eric Hodel]

given:

test.rb :

require 'b'

b = B.new

b = A::B.new

lib/base.rb:

module A
class Base
end
end

lib/b.rb:

require 'base'

module A
class B < Base
end
end

Why do I get

./lib/b.rb:2: uninitialized constant A::Base (NameError)
from test.rb:1:in `require'
from test.rb:1

?

This is a stripped down version of what I want to do (ie organize
my code into a module, but still keep classes in separate files,
have a base class and inherit).

It's probably something trivial, but at the moment I'm stuck - any
help would be (as always) greatly appreciated

Also you can get away with less indentation:

$ cat base.rb
module A; end

class A::Base
end
$ cat b.rb
require 'base'

class A::B < A::Base
end

 

[Christophe Grandsire]

Selon Kev Jackson :

given:

test.rb :

require 'b'

b = B.new


lib/base.rb:

module A
class Base
end
end

lib/b.rb:

module A
class B < Base
end
end


Why do I get

./lib/b.rb:2: uninitialized constant A::Base (NameError)
from test.rb:1:in `require'
from test.rb:1

?

In lib/b.rb, you need to write:
require "base"
module A
class B < Base
end
end

otherwise your code in b.rb isn't aware of base.rb, and thus doesn't
know about A::Base.
--
Christophe Grandsire.

http://rainbow.conlang.free.fr

You need a straight mind to invent a twisted conlang.

 

[Kev Jackson]

In lib/b.rb, you need to write:

require "base"
module A
class B < Base
end
end

otherwise your code in b.rb isn't aware of base.rb, and thus doesn't
know about A::Base.

require 'base'

causes

/lib/b.rb:1:in `require': No such file to load -- base (LoadError)
from ./lib/b.rb:1
from test.rb:1:in `require'
from test.rb:1

which is weird as I have done this before with other files, it's just
this one that it won't find

 

[Eric Hodel]

In lib/b.rb, you need to write:



require 'base'

require 'lib/base' then

 

[Kev Jackson]

In lib/b.rb, you need to write:



require 'base'

causes

./lib/b.rb:1:in `require': No such file to load -- base (LoadError)
from ./lib/b.rb:1
from test.rb:1:in `require'
from test.rb:1

which is weird as I have done this before with other files, it's just
this one that it won't find

in fact from test.rb, I can require 'lib/base', but from b.rb I can't
require 'base' (with b.rb and base.rb in the same directory) - this is
very strange behaviour

Kev

 

[daz]

given:

test.rb :

require 'b'

b = B.new


lib/base.rb:

module A
class Base
end
end

lib/b.rb:

module A
class B < Base
end
end


Why do I get

/lib/b.rb:2: uninitialized constant A::Base (NameError)
from test.rb:1:in `require'
from test.rb:1

?

This is a stripped down version of what I want to do (ie organize my
code into a module, but still keep classes in separate files, have a
base class and inherit).

It's probably something trivial, but at the moment I'm stuck - any help
would be (as always) greatly appreciated

Kev

Hi Kev,

require 'b' loads /and runs/ b.rb immediately.
You have at the top:

module A
class B < Base
end
end

Base is defined later, so you need to organise the require order (?).
Then b = A::B.new (as Eric said)

HTH,

daz

 

[Kev Jackson]

require 'lib/base' then

Thanks, this fixes it - but the actual path 'lib/base' is incorrect in
the context of the file b.rb (b.rb is in the same directory as base.rb,
therefore the line should be require 'base' no?)

Kev

 

[Eric Hodel]

Thanks, this fixes it - but the actual path 'lib/base' is incorrect
in the context of the file b.rb (b.rb is in the same directory as
base.rb, therefore the line should be require 'base' no?)

The load path works from Dir.pwd, not the paths of the files you
require.

ruby -Ilib will allow things to Just Work.

 

[Christophe Grandsire]

in fact from test.rb, I can require 'lib/base', but from b.rb I can't
require 'base' (with b.rb and base.rb in the same directory) - this is
very strange behaviour

Oops! Of course. "require"'s lookup system bit me again. IIRC it uses
$LOAD_PATH, which contains the usual standard lib directory roots, as wel=
l as
the directory of the file first run by Ruby (AFAIK). It *doesn't* contain=
the
path of library files you may also require. So you have to do require
'lib/base' everywhere.

Is there a good reason for this behaviour? There was a RCR to make the re=
quire
load path relative to the currently executing file (rather than only the
originally executing file), but it is branded 'obsolete' and I haven't se=
en it
rewritten, not even in the rejected RCRs. It's currently here:
http://www.rcrchive.net/rcr/show/170
Wouldn't it be a good idea to revive it?
--
Christophe Grandsire.

http://rainbow.conlang.free.fr

It takes a straight mind to create a twisted conlang.