Using Class Variables

Rails
1

Hello,
I haven’t used class variables before (I’m new to RoR and OOP in
general…) and I think I need to use them for part of my program. I
have several different views for my controller “compare”. For each view,
I need to grab the number of rows corresponding to several particular
SQL statements. I was thinking I could do something like this:

class CompareController < ApplicationController
@number_of_rows = Table.connection.select_all("
SELECT
COUNT(*) AS n
FROM table")
@@numofrows = @number_of_rows.to_s.slice(1,3).to_i

def index
etc…

Then use @@numofrows in the view like so:

<%= link_to “entries (#{@@numofrows})”, :controller => ‘compare’,
:action => ‘index’ %>

Obviously, this doesn’t work. I am new to this type of programming and I
am trying to read up on all of this, but I am still very confused on how
to do this type of thing…

Any help is appreciated!

Thank you,

  • Jeff M.
2

Nevermind, I dumped the class variable idea and now am using globals
instead, since they don’t need to be initialized.

Thanks,

  • Jeff
3

Hi,

I’m not sure I know enough about what you want to do, but I suspect that
neither class variables nor globals are a good solution. They almost
never
are.

If you want the count of rows in some table named “Table,” then you can
obtain it with Table.count. You could store this in an instance
variable,
which will be available in your views. For example, in your controller,

def some_action
@row_count = Table.count
end

And in your view,

<%= link_to “entries (#{@row_count})”, :controller => ‘compare’, :action
=>
‘index’ %>

If you find yourself fetching the row count in several actions, you
could
investigate using a before_filter.

Good luck,
Craig

4

Hello,

I advice you to use your model when you run any operation for your
database.

Here is my code, i hope it can help you.

CONTROLLER

class CompareController < ApplicationController

def index
…
end

def count_row
@number_of_rows = Table.lets_count_row
@slicing = @number_of_rows.to_s.slice(1,3).to_i
end

#if you want execute it in any pages of your view in this controller
#you can do like it

def my_page
count_row
end

…

end

YOUR TABLE MODEL

class Table < ActiveRecord::Base

def lets_count_row
self.count
end

OR

def lets_count_row
self.count_by_sql(“select count(*)from tables”)
end

…

end

YOUR VIEW count_row.rhtml

<%= link_to “entries (#{@slicing})”, :controller => ‘compare’, :action
=> ‘index’ %>

If you want run def count_row to entire controller, you should put def
count_row in application.rb, and you not need rewrite def count_row in
any controller. Example:

application.rb

class ApplicationController < ActionController::Base

def count_row
@number_of_rows = Table.lets_count_row
@slicing = @number_of_rows.to_s.slice(1,3).to_i
end

end

any_name_controller.rb

class AnyName < ApplicationController
before_filter :count_row
…
end

and the view is the same way and it could be used to any view from any
controller.

~~~~~**~~~~~
Reinhart Ariando
YM : Booking2Heaven
WEB : http://teapoci.blogspot.com