# Global variable in ruby **URL:** \ **Category:** Ruby\ **Created:** [April 10, 2010, 3:21am UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633 "2010-04-10T03:21:49Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![amishera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/59ef9b/32.png) [@amishera](https://www.ruby-forum.com/u/amishera)\ **Post date:** [April 10, 2010, 3:21am UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633/1 "2010-04-10T03:21:49Z")
Trying to use some global variable $buffer = Array.new 4 5 def save\_log(data, file\_name) 6 puts ‘save log called ‘+file\_name 7 open(file\_name, ‘w’) { |f| f.write(data) } 8 end 9 10 def get\_citations\_from\_page(data, start\_point, end\_point) 11 citations = get\_substring\_within\_inclusive(data, start\_point, end\_point) 12 u\_arr = getURLsFromPage(‘[http://www.xxxx.com/](http://www.xxxx.com/)’, citations) 13 u\_arr.each { 14 |t| 15 if (!beginsWith(t[1],‘[XXXX](http://www.xxxx.com//gp/reader)’)) 16 buffer.push t[0]+’%%%’+t[1] 17 end 18 } 19 end getting error: xxxx\_citations.rb:16:in `get_citations_from_page': undefined local variable or method `buffer’ for main:Object (NameError) from xxxx\_citations.rb:13:in `each' from xxxx_citations.rb:13:in `get\_citations\_from\_page’ from xxxx\_citations.rb:26:in `retrieve_citations' from xxxx_citations.rb:46 from xxxx_citations.rb:42:in `open’ from xxxx\_citations.rb:4 Why? How to solve it? ---
**Author:** ![amishera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/59ef9b/32.png) [@amishera](https://www.ruby-forum.com/u/amishera)\ **Post date:** [April 10, 2010, 3:34am UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633/2 "2010-04-10T03:34:45Z")
On Apr 9, 2010, at 6:21 PM, Amishera Amishera wrote: > 11 citations = get\_substring\_within\_inclusive(data, > > Why? How to solve it? Maybe because you meant $buffer ? 😉 ---
**Author:** ![amishera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/59ef9b/32.png) [@amishera](https://www.ruby-forum.com/u/amishera)\ **Post date:** [April 10, 2010, 4:48am UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633/3 "2010-04-10T04:48:44Z")
Amishera Amishera wrote: > Trying to use some global variable > > $buffer = Array.new While global variables are really nice, most programmers try not to use them, as they cause a lot of errors in the long end, dealing with other programs or add-ons. I try not to use Global Variables in my programs, but when I do need to, I name them so specifically, that they can not be confused with another program’s global variables. i.e. $program\_name\_buffer00 = Array.new ---
**Author:** ![amishera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/59ef9b/32.png) [@amishera](https://www.ruby-forum.com/u/amishera)\ **Post date:** [April 10, 2010, 10:54pm UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633/4 "2010-04-10T22:54:29Z")
Amishera Amishera wrote: > Trying to use some global variable > > $buffer = Array.new > 4 > 5 def save\_log(data, file\_name) > 6 puts 'save log called '+file\_name > 7 open(file\_name, ‘w’) { |f| f.write(data) } > 8 end > 9 > 10 def get\_citations\_from\_page(data, start\_point, end\_point) > 11 citations = get\_substring\_within\_inclusive(data, > start\_point, end\_point) > 12 u\_arr = getURLsFromPage(‘[http://www.xxxx.com/](http://www.xxxx.com/)’, citations) > 13 u\_arr.each { > 14 |t| > 15 if > > > (!beginsWith(t[1],‘[XXXX](http://www.xxxx.com//gp/reader)’)) > > 16 buffer.push t[0]+‘%%%’+t[1] > > 17 end > > 18 } > > 19 end The reason this is happening is because you forgot to write $ in buffer.push. It should be $buffer.push. But you could just put a buffer var to get passed into the function. > 10 def get\_citations\_from\_page(data, start\_point, end\_point, buffer) and then just write buffer for the last argument. ---
**Author:** ![amishera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/59ef9b/32.png) [@amishera](https://www.ruby-forum.com/u/amishera)\ **Post date:** [April 10, 2010, 8:06pm UTC](https://www.ruby-forum.com/t/global-variable-in-ruby/186633/5 "2010-04-10T20:06:03Z")
Jesse J. wrote: > > $buffer = Array.new > > While global variables are really nice, most programmers try not to use > them, as they cause a lot of errors in the long end, dealing with other > programs or add-ons. I try not to use Global Variables in my programs, > but when I do need to, I name them so specifically, that they can not be > confused with another program’s global variables. > > i.e. $program\_name\_buffer00 = Array.new If it’s just that a number of methods want access to the same buffer, you probably want to put them in a class and use an instance variable. class PageParser attr\_reader :buffer def initialize(buffer = []) @buffer = buffer end def get\_citations\_from\_page(data, start\_point, end\_point) citations = get\_substring\_within\_inclusive(data, start\_point, end\_point) u\_arr = getURLsFromPage(‘[http://www.xxxx.com/](http://www.xxxx.com/)’, citations) u\_arr.each { |t| if (!beginsWith(t[1],‘[XXXX](http://www.xxxx.com//gp/reader)’)) @buffer.push t[0]+‘%%%’+t[1] end } end def get\_substring\_within\_inclusive … end end parser = PageParser.new parser.get\_citations\_from\_page(…) p parser.buffer If you really want a single buffer which is global to the whole program, then I’d say an instance variable of a Class is the way to go, which avoids the global variable namespace problem. class PageParser @buffer = [] def self.buffer @buffer end end PageParser.buffer \<\< “hello” PageParser.buffer \<\< “world” p PageParser.buffer In the above code, @buffer is an instance variable of the Class object, not of instances of class PageParser (since class PageParser is itself an object)