Accessing class variables in views - ruby-on-rails-4

Question

What is the correct syntax for storing something in my class variable from a view ? Let's say that this is the code:
Controller:
class FooController < ApplicationController
##myvar = "I'm a string"
*
*
*
methods
*
*
*
end
Form:
<%= form_for(#something) do |f| %>
<%= f.text_field :myvar %>
<%= f.submit %>
<% end %>
This is just an example of a form as it is not functional, I cannot find what the correct syntax is for accesssing ##myvar from the view. Thanks !

Answer 1

as on request i edited, including attr_accessor
Rails way. Ill just fly over, hope you get it. you defenitely need to read more introductions to rails and its concept.
you have a rails-model, lets call it Animal
class Animal < ActiveRecord::Base
attr_accessor :non_saved_variable
end
this is having a database-table, lets say in this table we store race, name and age.
now we need a controller, to create/edit/update/delete animals
class AnimalController < ActionController::Base
def new
# this creates a new animal with blank values
#animal = Animal.new
end
end
now you need to go into your routes.rb and create a route for animals
resources :animal
this will create all (restful) routes for every actions of an animal.
now you need to have your template to render a form
form_for is a rails helper, to create a form, associated with the #animal (which is a new Animal). You pass |f| into the block, so with f you can access the form
=form_for #animal do |f|
then you can go for each field you need to call another rails helper
you can also access attr_accessors.
=f.text_field :race
=f.text_field :name
=f.text_field :age
=f.text_field :non_saved_variable
by that you get the stuff
dont fortget f.submit because your form needs a submit button
if you now click on your button, the form will be posted to the create method of rails. so you need to bring it into your controller
def create
# create a new animal with the values sended by the form
#animal = Animal.new params[:animal]
# here you can access the attr_accessor
#animal.do_something if #animal.non_saved_variable == "1337"
if #animal.save
# your animal was saved. you can now redirect or do whatever you want
else
#couldnt be saved, maybe validations have been wrong
#render the same form again
render action: :new
end
end
i hope that gave you a first insight of rails ?!

Answer 2

DO NOT DO THIS
You can get or set class variables from any class by:
<%= FooController.class_variable_get(:##myvar) %>
<%= FooController.class_variable_set(:##myvar, 'value') %>
This is probably not what you want. Do not do it. What are you trying to achieve?
DO THIS INSTEAD:
If it's a variable that you want to be available to all actions in that controller consider an instance variable set in a a before filter:
class FooController < ApplicationController
before_filter :set_var
private
def set_var
#my_var = "I'm a string"
end
end
Then in your view, just call <%= #my_var %>