Where to put require

Ruby
1

If I have a rails app and I need to put in
require ‘xxx’
include yyy

in my class ApplicationController < ActionController::Base

Where within this application.rb file do I put these lines? Thanks, Ike

2

On 10/20/06, Ike [email protected] wrote:

If I have a rails app and I need to put in
require ‘xxx’
include yyy

in my class ApplicationController < ActionController::Base

Where within this application.rb file do I put these lines? Thanks, Ike

It’s usually best to put it in the first lines of the file, before any
variable declarations or class definitions. They’re a bit like C’s
“” or Java’s “imports”.

3

On 10/20/06, Bira [email protected] wrote:

variable declarations or class definitions. They’re a bit like C’s
“” or Java’s “imports”.

And be careful where you place include Yyy as the placement influences
where the module will be mixed in.

It’s different when you do

include Forwardable
class X
…
end

and

class X
include Forwardable
…
end

Sometimes (=rarely), when you want to require later or not at all,
it’s useful to put require inside a method.

4

Bira’s kind of right, kind of wrong.

Java imports are package based, which while there is the file system
relation, is trying to keep developers from worrying about file paths.

Ruby requires work like C/C++ #includes. They are purely path related.
However, Ruby does have a system variable available, $:, that is the
PATH,
so you can do something like this:

$: << ‘…/…/lib/’
require ‘some_class_in_lib’

instead of
require ‘…/…/lib/some_class_in_lib’

You’ll see this type of syntax alot with libraries like Rails, who try
to
make everything available without any dealings with file or package
paths.

Jason

5

Jan S. wrote:

Sometimes (=rarely), when you want to require later or not at all,
it’s useful to put require inside a method.

Just to make it a little clearer, by experimenting you can see:

def check
a = [‘foo’, ‘bar’, ‘baz’] * 2
begin
a.each_slice(3) {|slice| p slice}
rescue Exception
puts “No such method\n”
end
require ‘enumerator’
a.each_slice(3){|slice| p slice}
end

#Test starts here

begin
x.each_slice(3) {|slice| p slice}
rescue Exception
puts “No such method\n”
end

puts $".include?(‘enumerator.so’)

check

puts $".include?(‘enumerator.so’)

x = [‘foo’, ‘bar’, ‘baz’] * 2
x.each_slice(2) {|slice| p slice}

Produces ->
No such method
false
No such method
[“foo”, “bar”, “baz”]
[“foo”, “bar”, “baz”]
true
[“FOO”, “BAR”]
[“BAZ”, “FOO”]
[“BAR”, “BAZ”]

As you can see, ‘require’ is itself a method (btw, mixed with the
require method of rubygems/custom_require.rb if specified), that calls
a library and adds it to $". Such library is called the first time is
required. So, as Jan said, you may call it anywhere on your program
depending on where do YOU require it.