What's the :: symbol on Geom::....

abakobo

hi everybody, i'm new on the forum!

thanks for the time you spend on forum's...

here's my question

what's behind the :: symbol in Geom?

ex:
*line1 = [Geom::Point3d.new(0,0,0), Geom::Vector3d.new(0,0,1)]
line2 = [Geom::Point3d.new(0,0,0), Geom::Vector3d.new(0,0,100)]

0,0,0 on each line should be closest because both lines start from

that point

pts = Geom.closest_points line1, line2*

and when do we use :: and/or . to call a method
is it only when using new or is it more subtle?

grtz

abakobo

TIG

Best not to think about it too much...
Just follow the usual conventions [some are interchangeable ]...

Geom and Sketchup
are examples of a 'module'...

Geom::Transformation and Sketchup::Face
are examples of a class [this uses a :: separator]

Geom.intersect_line_plane() and Geom::Transformation.translation()
is a method (def) [this uses a . separator]

Sketchup::Face::PointUnknown
is a Fixnum [this is a Constant that is used in face.classify_point result tests]

You can also use it to return a module's @var reference's value, but only if a suitable 'attr_accessor' has been setup in the code...
For example: TIG::MyXtool.xyz
[this is a module containing a module, with a :: separator, then a . to give the reference]

Tip:
Modules and Classes will start with a Capital letter.
Methods etc will start with a lower case letter.

Dan Rathbun

@abakobo said:

what's behind the :: symbol in Geom ?

It is called the scope operator.

:: with nothing to the left of it means the top level scope (aka TOPLEVEL_BINDING,) which is "a particular instance of Object called 'main'".
But it's use that way is optional. Ruby always checks the current scope first, then the top level scope if it needs to.

But this is also why you should always be executing YOUR code inside a toplevel module, with some unique name that you invent. like
module Abakobo

So Geom::Point3d is referring to the Point3d class, within the Geom module scope.

@abakobo said:

and when do we use :: and/or . to call a method

It's style, but many people only use the . for ALL methods.

Some people use :: for calling module functions and class methods (which the new constructor is,) and then use . to call only instance methods. (Some of the older examples, from the days when SketchUp was owned by Google or @Last Software, use this latter convention. I guess they wanted to emphasize the calling of class methods or module functions.)