Identify/locate the Subclass

Anton_S

During coding I came up to the point where I needed to figure whether the selected object is a sublcass of a class. I mean like Sketchup.active_model.select_tool only accepts subclasses, right? And it only works if the tool includes some of its methods, such as onMouseMove.

I can predict how it works. Maybe it uses @selected_tool.include?(certain_method), If method not inclduded, then the tool jst ignores the callback to current message. But with this assumption the ...select_tool method will also accept anything, but not nil, as it describes in the API description.

Is there a way to actually know whether the selected tool is actually a subclass of a class?

Dan Rathbun

Specifically.. about SketchUp API Tool classes:

There is NO defined Tool superclass.

That means that your custom tool class definition will be a subclass of Object.

Now, because of that.. Sketchup.active_model.select_tool() does NOT do any typechecking, other than to check if a nil argument was passed.

So.. when you pass an object to Sketchup.active_model.select_tool() (and it's not nil,) SketchUp expects it to have the minimum of the Tool class callbacks. (I think activate would be the minimum.)

To ask an object if it has a public activate method:

obj.respond_to?(:activate)

Dan Rathbun

About classes in general:

The logical methods can apply at the class level.

For instance, class Class, is a subclass of class Module.

so: Class < Module returns true

and: Class > Module returns false

further, Object is THE supreme class, the common progenitor of all other classes.
so: Class > Object returns false
and Object is always greater than any other class.

So IF you decide to set up your own tool protoclass... Anton::Tool
and you wanted to see if a specific tool instance was a subclass:

nifty_tool.is_a?(Anton::Tool)
or
nifty_tool.class < Anton::Tool

... would return true, if nifty_tool's class was a descendant class of Anton::Tool.

If you wanted to see a list of nifty_tool's ancestors:
puts nifty_tool.class.ancestors

Anton_S

@dan rathbun said:

obj.respond_to?(:activate)

Thanks Dan, description - sure will help.

Edited: Previously, I used obj.methods.include?(someMethod). - That will give an error if the object wouldn't be a class, nor module. But using respond_to? will work on any selected object without errors. Jst true or false

I was wrong in blue words. Actually, .methods can be implemented in any object. 134.methods, nil.methods, "dsfg".methods, false.methods, Class.methods will always work.