Help Understanding Classes and Class objects

[TIG]

Try this change: in the EndPulley code after
self.create_geometry
###ADD
return @group

as the last code before the ' end' of the initialize...

REMOVE the equivalent line from the create_geometry method...

Run with the ' puts' to see what's what now...

[pmagans]

Same message No change - its dying on the puts statements?

[Dan Rathbun]

WAIT !!

Earlier on I attempted to explain that his custom classes were WRAPPER CLASSES. (And questioned why anyone would want to actually do this. Subsequent edits by a user such as boolean operations can cause the references held by the wrapper class instances to become invalid and point at Sketchup::DeletedEntity objects.)

I showed an example which did NOT have a EndPully class, because it would ALSO be a wrapper class, whose new() constructor returns the wrapper instance NOT a Sketchup::Group instance.

SO.. therefore... he needs to call the EndPully instance's group() wrapper method (created via the attr_reader(:group) call,) which will return the actual group reference:
st_ep.group.transform! t1

[TIG]

Can you also add the equivalent 'puts' just after the
st_ep = EndPulley.new(@group, @st_point)

puts 'st_tp details...' puts st_tp puts st_tp.class puts st_tp.name puts 'END'

so we can see what the first part does...

[Dan Rathbun]

Sorry ... I got busy and did not get back to this thread,

I was going to continue the discussion on why wrapper classes are extremely problematic for Sketchup::Drawingelement subclasses. (One issue is on Mac multiple models could be open, but the API does not yet have a good way to track them, and we know of some bugs on the PC, that causes issues.)

---

Anyway... the alternative you REALLY should be using is to create a Sketchup::ComponentDefinition for your pully and conveyor, and then place instances of these (rather than Groups.)

The definition's instances collection will keep track of them for you.

The model's DefintionList collection will keep track of your definition(s) for each model that they are inserted into.

When a model is opened, your plugin can search through it's DefintionList to find those definitions that are "known" to the plugin. And then grab an array of their instances, and iterate it to get references.

[pmagans]

Dan you are correct. Adding the .group gave me access to the "group" objects that were created.

As for my thought process I am not sure that it is valid so let me describe my thoughts.

I don't want to code "like" things so I assumed that using classes would allow me to inherit class attributes things without having to copy a bunch of code it multiple places. For example classes would be:

1. FUNCTIONAL AREAS
   [list:11tc2ay1]1. CONVEYOR

• CONVEYOR_COMPONENTS

• END_PULLEY

• DRIVE

• INTERMEDIATE_BED

• PAN_GUARD

• BEARINGS

• ETC.

• BUILDING_MODSETC.[/*11tc2ay1][/list11tc2ay1]Later I could write Customer specific code for each of the classes and inherit all of the functionality that I wrote in the "General" Classes

One customer's end_pulley may contain different bearings, pulleys, profiles etc. Also there are many types of end pulleys. That being said they do have some similarities especially attribute definitions, layer structure, basic functionality.

Am I on the right track or am I way off the rails?

[Dan Rathbun]

@TIG

Simply put:

A class constructor returns an instance of IT's class.

CONVEYOR::EndPully.new() returns an instance of CONVEYOR::EndPully not an instance Sketchup::Group

This is one of the MAJOR drawbacks of a wrapper class, you have to write wrapper methods for all the methods of the wrapped object that you wish to access "as if" the wrapper "were" the object itself.

There are some ruby tricks to get a list of only the API methods, and define wrapper methods via an eval loop. But .. it's still can get complicated in other nitty-gritty ways.

I just do not recommend it.

[Dan Rathbun]

Dynamic Component definitions can give you a lot of flexibility. A style of pully, were the diameter and width are settable via the Component Options dialog.

Your code classes and modules... are geometry creators, but not the actual model objects themselves.

You can also inherit (share) code functionality via mixin module libraries.

Given a mixin module named BasicPully ...

module FancyPully

  include BasicPully

  # now overrride inherited methods if desired

  # now add additional methods if desired

end

.. and later ...

module NiftyPully

  include FancyPully

  # now overrride inherited methods if desired

  # now add additional methods if desired

end

[TIG]

doh!

[pmagans]

I will check into the mixin module approach also the dynamic components. Are dynamic components "create-able" through Ruby code or only through the Sketchup interface?

The only info/tutorial I could find was:
http://sketchucation.com/forums/viewtopic.php?f=180&t=17888&p=145120&hilit=dynamic+component+tutorial#p145120

[Dan Rathbun]

Both.

But of course the coding means is not documented because the Free license users are not supposed to do it. (... or at least use a wizard interface.)

A lot has been written about them.

[pmagans]

@dan rathbun said:

But of course the coding means is not documented because the Free license users are not supposed to do it. (... or at least use a wizard interface.)

That's a bummer. I like the concept of dynamic tools for locking up variables and documenting the components, but I hate the user interface! It would just take me too long through traditional means to create a workable library. And of course if I wanted to change something I would have to do it in multiple places. I will do a more active search for creating/modifying dynamic components through Ruby. So far what I have found has not been that helpful besides holding/setting attributes. Any tips on where to start?
Thanks!

[Dan Rathbun]

In SU Pro.. open the "Component Attributes" wizard.

Switch to the "Functions" pane.

Click on the "more >>" link, ... a bowser window will open to the DC online reference.

Bookmark that page.

Notice also the links in the left navigation column.

Happy Reading.

Basically scripting them is first understanding how to create and access Attribute Dictionary objects.

[pmagans]

@dan rathbun said:

Bookmark that page.

Done, thanks for the link.

I remember doing the tutorials when DC's first came out but have forgotton the majority of what I learned so I guess I will be spending some time there first.