# Re: openstruct oddity **URL:** \ **Category:** Ruby\ **Created:** [December 7, 2006, 10:13pm UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693 "2006-12-07T22:13:08Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 7, 2006, 10:13pm UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693/1 "2006-12-07T22:13:08Z")
> This is surely an anomaly too, is it not? > Pardon my ignorance. I wasn’t aware that the mixin module at top level > causes all its methods become globally available for all levels below. > Although, some comment on the explanation or reason behind this is > appreciated. (I was trying to turn my script into some script type by > mixin > a module. Doesn’t look like a good idea now) -andre ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 9, 2006, 9:53am UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693/2 "2006-12-09T09:53:04Z")
On 12/8/06, Andreas S [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Pardon my ignorance. I wasn’t aware that the mixin module at top level > causes all its methods become globally available for all levels below. > Although, some comment on the explanation or reason behind this is > appreciated. At the top level, the “current object”, self, is a particular instance of Object (which I’ll call ‘main’). Now, main has some methods in its singleton class. Let’s take a peek: g@crash:~/tmp$ ruby -e ‘p self.methods(false)’ [“public”, “include”, “to\_s”, “private”] So, when you do “include Foo” at the toplevel, this is, as always, the same as “self.include(Foo)”, which means call main’s singleton class method #include. This is defined to include things into Object. Since everything derives from Object, the value of self at any point in your code will be an Object, and so you can call Foo’s methods without a receiver. Clever, huh? Along a similar vein, ruby has the notion of the “current class”. This is like self in that it is defined at any point in your code, but there’s no short identifier for it. In fact, I can’t think of a (non-destructive, thread-safe) expression that will return it. But this is the class that will gain a new method when you do “def foo”. So, at the toplevel, the “current class” is Object (not to be confused with self, which is main). The current visibility is also “private”, so #foo will be a private method on Object. This lets you call #foo from anywhere (again, because self will always be an Object), but will cause an error if you do 3.foo or something, since #foo is private and therefore can only be directly called without a receiver. You can, incidentally, make the toplevel methods public. That’s what the #public is for up there in main’s singleton class. Also note that in irb, the default toplevel visibility is public, not private. (Although I’ve noticed using a different context-mode, e.g., ‘irb –context-mode 0’ changes this. Context modes are a whole other novel, however, and should probably be explained by someone who knows more than me. I invite them ;-). Anyway, I know this is more than you asked for, but it took me a hunt around the source a while ago to get to the bottom of it. So maybe I can spare you, or someone else, the trek. > (I was trying to turn my script into some script type by mixin > a module. Doesn’t look like a good idea now) Sorry, I don’t understand what you mean. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 9, 2006, 9:57am UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693/3 "2006-12-09T09:57:04Z")
On 12/9/06, George O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Along a similar vein, ruby has the notion of the “current class”. > This is like self in that it is defined at any point in your code, but > there’s no short identifier for it. In fact, I can’t think of a > (non-destructive, thread-safe) expression that will return it. But > this is the class that will gain a new method when you do “def foo”. .gsub(/class/, ‘module’) # 😛 ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 9, 2006, 2:21pm UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693/4 "2006-12-09T14:21:20Z")
George O. wrote: > Clever, huh? > > Along a similar vein, ruby has the notion of the “current class”. > This is like self in that it is defined at any point in your code, but > there’s no short identifier for it. In fact, I can’t think of a > (non-destructive, thread-safe) expression that will return it. But > this is the class that will gain a new method when you do “def foo”. The current class (or module - I saw your correction) is in “self” when you are outside a “def” or . It is just another object (of class “Class” or “Module” respectively). Try this: class Foo p self p self.class end module Foo p self p self.class end If you are inside a “def” then it is “self.class”, but in that case “self.class” will refer to the class of the object you call the method on, not the class or module the object was defined in. Vidar ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 14, 2006, 5:52am UTC](https://www.ruby-forum.com/t/re-openstruct-oddity/78693/5 "2006-12-14T05:52:54Z")
On 12/10/06, Vidar H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > “Class” or “Module” respectively). > p self.class > end > > If you are inside a “def” then it is “self.class”, but in that case > “self.class” will refer to the class of the object you call the method > on, not the class or module the object was defined in. You’re correct (well, almost), but that’s two expressions… ;-). And ones where you have to know the context up front (statically). It falls short on instance\_eval. Inside an instance\_eval block, the current module is self’s singleton class. But I was just making the point that there is this bit of state that exists on the C-side that isn’t so clearly visible on the ruby one. And that was, I think, the source of my confusion until I looked into it.