How to avoid multiple inclusion of a file

ruby-talk
1

Hi

My program is split up into multiple files, each containing a set of
related class definitions. In the main file, all these files are
included by using require. But how can i avoid multiple inclusion of a
file by mistake.

Is there anything similar to C languages #ifndef .......

thanks
suresh

2

As long as the require lines are exactly the same, there's nothing to
worry about.

file1.rb:
require 'lib'

file2.rb:
require 'lib'

This will work fine. You will run into problems if you put relative
paths though:

file1.rb:
require 'lib'

lower/file3.rb:
require '../lib'

This will end up require-ing lib.rb twice, and possibly cause problems.

Either use full paths, or add directories to the $LOAD_PATH to protect
against this.

Jason

···

On Wed, Jun 11, 2008 at 12:24 PM, suresh <suresh.amritapuri@gmail.com> wrote:

Hi

My program is split up into multiple files, each containing a set of
related class definitions. In the main file, all these files are
included by using require. But how can i avoid multiple inclusion of a
file by mistake.

Is there anything similar to C languages #ifndef .......

thanks
suresh

3

unless defined? A

   require 'a'

end

a @ http://codeforpeople.com/

···

On Jun 11, 2008, at 10:24 AM, suresh wrote:

Is there anything similar to C languages #ifndef .......

--
we can deny everything, except that we have the possibility of being better. simply reflect on that.
h.h. the 14th dalai lama

4

Hi Jason,

Will tell you what happened to me. I had some database populating code
in some import class definitions. By mistake that file got included
twice and I had to spend a lot of time to figure out how this
happened. So thats why my question, how can I avoid multiple inclusion
of files.

suresh

···

On Jun 11, 9:28 pm, Jason Roelofs <jameskil...@gmail.com> wrote:

As long as the require lines are exactly the same, there's nothing to
worry about.

file1.rb:
require 'lib'

file2.rb:
require 'lib'

This will work fine. You will run into problems if you put relative
paths though:

file1.rb:
require 'lib'

lower/file3.rb:
require '../lib'

This will end up require-ing lib.rb twice, and possibly cause problems.

Either use full paths, or add directories to the $LOAD_PATH to protect
against this.

Jason

On Wed, Jun 11, 2008 at 12:24 PM, suresh <suresh.amritap...@gmail.com> wrote:
> Hi

> My program is split up into multiple files, each containing a set of
> related class definitions. In the main file, all these files are
> included by using require. But how can i avoid multiple inclusion of a
> file by mistake.

> Is there anything similar to C languages #ifndef .......

> thanks
> suresh

5

I just told you how to avoid it. If you're getting collisions, then
you're doing what I've outlined above.

Jason

···

On Wed, Jun 11, 2008 at 12:34 PM, suresh <suresh.amritapuri@gmail.com> wrote:

On Jun 11, 9:28 pm, Jason Roelofs <jameskil...@gmail.com> wrote:

As long as the require lines are exactly the same, there's nothing to
worry about.

file1.rb:
require 'lib'

file2.rb:
require 'lib'

This will work fine. You will run into problems if you put relative
paths though:

file1.rb:
require 'lib'

lower/file3.rb:
require '../lib'

This will end up require-ing lib.rb twice, and possibly cause problems.

Either use full paths, or add directories to the $LOAD_PATH to protect
against this.

Jason

On Wed, Jun 11, 2008 at 12:24 PM, suresh <suresh.amritap...@gmail.com> wrote:
> Hi

> My program is split up into multiple files, each containing a set of
> related class definitions. In the main file, all these files are
> included by using require. But how can i avoid multiple inclusion of a
> file by mistake.

> Is there anything similar to C languages #ifndef .......

> thanks
> suresh

Hi Jason,

Will tell you what happened to me. I had some database populating code
in some import class definitions. By mistake that file got included
twice and I had to spend a lot of time to figure out how this
happened. So thats why my question, how can I avoid multiple inclusion
of files.

suresh

6

if you are writing the files that are included you can self-protect them

unlss defined? $mylib

module MyLib
end

end

however, if you expect something like rails or ramaze to autoload these files in development mode think twice.

a @ http://codeforpeople.com/

···

On Jun 11, 2008, at 10:34 AM, suresh wrote:

Hi Jason,

Will tell you what happened to me. I had some database populating code
in some import class definitions. By mistake that file got included
twice and I had to spend a lot of time to figure out how this
happened. So thats why my question, how can I avoid multiple inclusion
of files.

suresh

--
we can deny everything, except that we have the possibility of being better. simply reflect on that.
h.h. the 14th dalai lama