Class Variable

rubyonrails-talk
1

Hi everyone,

I have a question about class variable in Rails:

I have a class Point that contains an class variable @@color_points="green"

In a first web Page I want to set up this variable, hence i do Point.color_points = "green" then i test it using puts Point.color_points ( = green, it works,yes!) Then i have a link_to instruction that points to another web page. On this one (the other one), I just want to print Point.color_points, but now its value is "".

DOes anyone know why and could explain me?

2

Each request is isolated. At the end of the first request, all the variables you've set disappear into the ether. If you want something to persist, you need to store it - in the DB, the session, or somewhere else. The second request builds up new instances of all the objects - so the class variable is back to its default value.

3

thelo.g thelo wrote in post #1018888:

Hi everyone,

I have a question about class variable in Rails:

I have a class Point that contains an class variable @@color_points="green"

In a first web Page I want to set up this variable, hence i do Point.color_points = "green" then i test it using puts Point.color_points ( = green, it works,yes!) Then i have a link_to instruction that points to another web page. On this one (the other one), I just want to print Point.color_points, but now its value is "".

DOes anyone know why and could explain me?

In addition, you shouldn't be using class variables. You can forget they exist.

4

class Dog   @count = 0

  def initialize     Dog.count += 1   end

  def self.count     @count   end

  def self.count=(val)     @count = val   end

end

d1 = Dog.new puts Dog.count

d2 = Dog.new puts Dog.count

--output:-- 1 2

5

Bwah! Hahahah!

What tosh...

6

class Dog @count = 0

def initialize Dog.count += 1 end

def self.count @count end

def self.count=(val) @count = val end

end

If you want to be entirely nit-picky those are class instance variables rather than class variables.

Fred

7

Michael Pavling wrote in post #1018902: