Hi, I just wanted some clarification on this.
In production mode, while I know that object instance variables are
local to the object and so to the request, but is this same with class
variables and class instance variables or are they shared between
requests?
I have this question, because I know that classes are cached in
production mode. But what does this mean? Like, classes are
initialised and cached at the start of the server (and so are class
variables and class level instance variables) and are persistent in
the memory throughout, or it's like, just class definitions are cached
(so they are not read every time from the disk), and they are re-
initialised for every request, so that every request has its own set?
Say, in file `lib/example.rb` I have defined something like -
#lib/example.rb
module Example
class << self
def assign value
@@class_variable = value
@class_instance_variable = value
end
def read
[@@class_variable, @class_instance_variable]
end
end
end
#app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
before_filter :initialise
def initialise
Example.assign params[:name]
end
end
1. Request "A" comes with params[:name] as "a".
2. While request "A" executes, request "B" comes with params[:name] as
"b".
3. Now after arrival of request "B", if code in request "A" accesses
Example.read(), what would it return? ['b', 'b'], ['a', 'a'] or
(maybe, just maybe) ['a', 'b']?
I'd also like to write one more example -
#lib/example.rb
module Example
class << self
@@class_variable = 'default'
@class_instance_variable = 'default'
def assign value
@@class_variable =
@class_instance_variable = value
end
def read
[@@class_variable, @class_instance_variable]
end
end
end
1. Request "A" comes, executes Example.assign('a') and finishes.
2. Request "B" comes and tries to execute Example.read(), without
modifying the variables. What would it get? "default" or "a"?
PS: While writing, I felt like this is a silly question. I'm a novice,
anyway.
- thanks.
