class-variables

Active Resource can make use of HTTP authentication set at the class level. For instance: class Resource < ActiveResource::Base end Resource.user = 'user' Resource.password = 'password' or Resource.site = "http://user:password@site.com/" But what if I use different HTTP authentication based on which user is logged in? If I change Resource.user and Resource.password, is that going to cause a race condition where requests from one thread suddenly start using the authentication of a user whose requests are running simultaneously in a different thread? Or is this a non-issue (as long as I reset

The ruby class-instance stuff is giving me a headache. I understand given this... class Foo @var = 'bar' end ...that @var is a variable on the created class's instance. But how do I create a sub-class overridable class variable? Here is an example of what I would do in Python: class Fish: var = 'fish' def v(self): return self.var class Trout(Fish): var = 'trout' class Salmon(Fish): var = 'salmon' print Trout().v() print Salmon().v() Which outputs: trout salmon How do I do the same thing in ruby? To contrast @khelll's answer, this uses instance variables on the Class objects: class Fish # an

I was surprised to to learn that a class variable of a subclass can't access a class variable of the parent without specifically indicating the class name of the parent: >>> class A(object): ... x = 0 ... >>> class B(A): ... y = x+1 ... Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 2, in B NameError: name 'x' is not defined >>> class B(A): ... y = A.x + 1 ... >>> B.x 0 >>> B.y 1 Why is it that in defining B.y I have to refer to A.x and not just x? This is counter to my intuition from instance variables, and since I can refer to B.x after B is

What are Ruby variables preceded with double at signs ( @@ )? My understanding of a variable preceded with an at sign is that it is an instance variable, like this in PHP: PHP version class Person { public $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } } Ruby equivalent class Person def set_name(name) @name = name end def get_name() @name end end What does the double at sign @@ mean, and how does it differ from a single at sign? A variable prefixed with @ is an instance variable , while one prefixed with @@ is a class variable .