Wrong cloning of Sketchup::Color objects

fredo6

For information, there is an error in the way colors created as Sketchup::Color objects answer to the clone method.

Easy to reproduce in the Ruby console (all versions of SU, including SU2016)


c = Sketchup;;Color.new 'blue'
Color(  0,   0, 255, 255)
c.clone
Color(  0,   0,   0,   0)

This is annoying if you do not know the problem and duplicate hash arrays by cloning.

The workaround is simply cloned_color = Sketchup::Color.new(original_color).

But, I see no metaphysical reason why clone would not work correctly. It works fine on Point3d, Vector3d and Transformations. So I logged a bug to the Sketchup team.

Fredo

thomthom

hm... I think I ran into this myself. Might be an omission.

Btw, in regard to point3d and vector3d - one would normally use dup - but for some reason only clone was implemented for these classes and I think it acts like dup should have been.

driven

I use

 c = (Sketchup;;Color.new 'blue').to_a
# => [0, 0, 255, 255]
 c.dup
# => [0, 0, 255, 255]

can't remember why, but maybe for the same reason...

john

thomthom

c2 = Sketchup::Color.new(c1.to_a)

fredo6

The workaround is easy to find, but that was the bug which was more difficult to identify.

I still think it is a bug. Either Sketchup::Color does not support clone, or it does support correctly!

Fredo

thomthom

True that.

fredo6

Dan,

We know that most Sketchup objects won't behave correctly with clone or dup.

However, and wrongly, I thought Sketchup::Color was just an encapsulation of a 4-value array and would behave as Geom::Point3d or Geom::Transformation.

Now I know it's not the case and I can live with it, because I know.

Fredo

Dan Rathbun

@thomthom said:

hm... I think I ran into this myself. Might be an omission.

Yes, you did. You posted a public announcement in 2010:
http://sketchucation.com/forums/viewtopic.php?f=180%26amp;t=32591

@fredo6 said:

This is annoying if you do not know the problem and duplicate hash arrays by cloning.

The workaround is simply cloned_color = Sketchup::Color.new(original_color).

Which goes against the API documentation be inadequate (again.)

@fredo6 said:

It works fine on Point3d, Vector3d and Transformations.

Because the API explicitly overrides the clone() method inherited from object, in those three API classes.
http://ruby-doc.org/core-2.0.0/Object.html#method-i-clone

@fredo6 said:

But, I see no metaphysical reason why clone would not work correctly.

The Ruby interpreter follows precise "rules" of it's Object Oriented Programming model, .. so metaphysics (or abstract) reasons do not apply.

In the case of Ruby's clone and dup

@unknownuser said:

Ruby Doc: Object#clone()[/url:3ety1hw5]":3ety1hw5]This method may have class-specific behavior. If so, that behavior will be documented under the #initialize_copy method of the class.

So, a custom class needs to implement an #initialize_copy() method, in order to leverage Ruby's built-in cloning / dup'ing (so Ruby knows how to create the object copy,) or locally override the methods directly.

For examples of how arrays, hashes and strings are cloned see:

[url=http://ruby-doc.org/core-2.0.0/Hash.html#method-i-initialize_copy:3ety1hw5]#initialize_copy (Hash)[/url:3ety1hw5] [you must click to see the C source]

Just making an assumption, that is outside the "order of Ruby things" is bound to lead to failure or frustration.

So the historical correct assumption has been, "If API classes (especially those that are model entity classes,) have not published a specific cloning method overrides,.. then don't use clone() or dup() with them."

How do you know when API classes implement clone()?

Refer to the API method index for "c":
http://www.sketchup.com/intl/en/developer/docs/methods#index_c

@fredo6 said:

So I logged a bug to the Sketchup team.

Which I also did like 7/8 years ago. So, it is already logged.

Other old threads on this:
2010: http://sketchucation.com/forums/viewtopic.php?f=180%26amp;t=29138%26amp;p=253940#p253787
2011: http://sketchucation.com/forums/viewtopic.php?f=180%26amp;t=40201%26amp;p=355527#p355527
2014: http://sketchucation.com/forums/viewtopic.php?f=180%26amp;t=58083%26amp;hilit=clone%26amp;p=530348#p530015

Related... concerning lack of Geom::PolygonMesh clone() & dup() methods:
http://sketchucation.com/forums/viewtopic.php?f=180%26amp;t=58080%26amp;p=530014#p530014

Dan Rathbun

@fredo6 said:

However, and wrongly, I thought Sketchup::Color was just an encapsulation of a 4-value array ...

But that does bring up a very good point, that because it is compatible with an array (ie, has a to_a method and it's constructor accepts an array,)... making a clone method is beyond simple:

For Ruby 2.0+;

module Fredo6;;Cloner
  refine ;;Sketchup;;Color do
    def clone()
      self.class;;new(self.to_a)
    end
  end
end

using Fredo6;;Cloner

module Fredo6;;SomePlugin
  # code that uses refined Color class
end