Help with Components

Chris Fullmer

I like that Thom. I've also seen you use "select" a few times recently. I'll try to look at it, but is it different than collect? I recently ran across that one, and I never rememeber to use it. But they both appear to do about the same thing, and are remarkably useful for populating an array.

Chris

thomthom

@chris fullmer said:

I like that Thom. I've also seen you use "select" a few times recently. I'll try to look at it, but is it different than collect? I recently ran across that one, and I never rememeber to use it. But they both appear to do about the same thing, and are remarkably useful for populating an array.

Chris

They are not the same.

Enumerable.collect (alias Enumerable.map)

arr = [0, 1, 2, 3, 4] arr.collect { |i| i * 2 }
returns: [0, 2, 4, 6, 8]
I use it for instance to collect Point3ds from vertices collections.
points = face.vertices.collect { |vertex| vertex.position }

Enumerable.select (alias Enumerable.find_all)
arr = [0, 1, 2, 3, 4] arr.select { |i| i%2 > 0 } # block returns true if i is an odd number
returns: [1, 3]

I recently noticed this:

Enumerable.partition
arr = [0, 1, 2, 3, 4] arr.partition { |i| i%2 > 0 } # block returns true if i is and odd number
returns: [[1, 3], [0, 2, 4]]

Also rather handy.

The Enumerable module, which the Array class includes, has a number of very nice methods which I've found do many of the things I often do with arrays. I just haven't noticed them, partly because not everything in the Enumerable module isn't listed in the Array class docs.

model.selection.all? { |e| e.is_a?(Sketchup::Edge) }

or

[ruby:af7phbud]model.selection.any? { |e| e.is_a?(Sketchup::Edge) }[/ruby:af7phbud]

Chris Fullmer

Wow those are great Thom. I see the difference now there with collect and select. And I really like that partition method. Not sure where I'd use it right now, but I have a feeling it might come in handy eventually.

Thanks!

Chris

thomthom

Those five methods there has cut down many lines in my older codes.

honoluludesktop

Hi Guy, Finally got around to working on my program, and thanks to you it works. I have one question. How do I understand the following bit of code?

comp_new = comp_entities.select do |e| 
  e.is_a?(Sketchup;;Drawingelement)
end

Sorry for the long-hand, but it helps me to read my code, perhaps when I get better:-}

thomthom

your variable name is a bit confusing. "comp_entities" is the resulting array from .explode ? Assuming it is:

"comp_new" sounds like it's a ComponentInstance or ComponentDefinition, but in this case it will be a collection of entities.

Example of .select: arr1.select will return a new array will all the elements of arr1 when the block returns true.

In your case, you have an array returned from .explode. That array contains lots of thing you don't want. But the common denominator for the items you do want is that they inherit from the DrawingElement class. So we use the .select method to extract only the items that inherits from that class e.is_a?(Sketchup::Drawingelement).

thomthom

Yes.

When you see in the API manual, for the Face class for example: http://code.google.com/intl/nb/apis/sketchup/docs/ourdoc/face.html
Notice it says: Parent: Drawingelement

And the Drawingelement class says Parent: Entity

And the Loop class: Parent: Entity

So a Face
.is_a?(Sketchup::Face) == true
.is_a?(Sketchup::Drawingelement) == true
.is_a?(Sketchup::Entity) == true

But a Loop
.is_a?(Sketchup::Loop) == true
.is_a?(Sketchup::Drawingelement) == false <- Notice
.is_a?(Sketchup::Entity) == true

Because the relationship of a Face is:
Sketchup::Face < Sketchup::Drawingelement < Sketchup::Entity < Object

While a Loop is:
Sketchup::Loop < Sketchup::Entity < Object

thomthom

The Object Diagram is a nice graphical overview of the classes relationships: http://code.google.com/intl/nb/apis/sketchup/docs/diagram.html

thomthom

@honoluludesktop said:

Yes, "comp_entities" is the exploded array. OK, so when I see is_a? in this manner, the do loop is "select(ing) the entity(s)" in the array that is a (are) %(#FF0000)Sketchup::Drawingelement. Is it faster (better) then:

comp_entities.select do |e| 
>   if e.is_a? Sketchup;;Drawingelement
>     comp_new.push e
>   end
> end

In your examples, what you mean to do is:

comp_entities.each do |e| 
  if e.is_a? Sketchup;;Drawingelement
    comp_new.push e
  end
end

Notice the .each instead of .select

.each is a simple iterator - it does not return any values.
.select returns a new array - where the content depends on when the block yields true.


comp_new = []
comp_entities.each do |e|
  if e.is_a? Sketchup;;Drawingelement
    comp_new.push e
  end
end

Does the exact same thing as:


comp_new = comp_entities.select do |e|
  e.is_a?(Sketchup;;Drawingelement)
end

Can also we written as one line:


comp_new = comp_entities.select { |e| e.is_a?(Sketchup;;Drawingelement) }

There are many ways to do things - but Ruby has many useful methods for repeated tasks that saves your from typing the same code structure over and over again.
In these examples - I'm not sure if anyone is any significantly faster than the other. But .select saves some characters.

honoluludesktop

Opps, I meant comp_entities.each. Thanks for the lesson.

honoluludesktop

Yes, "comp_entities" is the exploded array. OK, so when I see is_a? in this manner, the do loop is "select(ing) the entity(s)" in the array that is a (are) %(#FF0000)Sketchup::Drawingelement. Is it faster (better) then:

comp_entities.each do |e| 
  if e.is_a? Sketchup;;Drawingelement
    comp_new.push e
  end
end

Addenda: Corrected as noted below.