Understanding a Script

Developers Ruby API
1

I came across this small script at Sketchucation which I’ve been trying to understand…

mod = Sketchup.active_model
sel = mod.selection
unless sel.empty?
  layers = []
  sel.to_a.each{|e|
    layers << e.layer
  }
  layers.flatten!;layers.uniq!
  mod.layers.each{|l|
    next if layers.include?(l)
    l.visible=false
  }
end

So…

layers = []

This is declaring an array called layers ?
And has nothing to do with the SketchUp Class Layers ?

sel.to_a.each{|e|
    layers << e.layer
  }

Here, each tag ( e.layer ) in the selection is put in the layers array ?

layers.flatten!;layers.uniq!

I think i understand what is happening here but not why.

mod.layers.each{|l|
    next if layers.include?(l)
    l.visible=false
  }

Here, the code is cycling through all the tags ( l ) in the model and if ( l ) is in the array layers it skips otherwise the tag ( l ) is turned off.

2

That is turning off all the layers except ones used by anything I’m the current selection. Setting layers= creates an empty Array. The name referring to the Array has nothing to do with the models layers yet, it is just a name to signify what is going to be put in the Array. The flatten and uniq are to eliminate any duplicates.

3

This is what was confusing me somewhat.

Thanks!

4

It could have been better named like: used_layers.

Yes, but I cannot see how a nested array would get pushed into the “used layers” array.
So, I think that the flatten! call is frivolous.

The actual term is making a reference assignment. The name “layers” is the reference name, and it is made to point at a new literal empty array. It is similar to doing …

layers = Array.new

There are several other things that are not needed. For example calling .to_a on the Selection object is unnecessary as that class has Enumerable mixed in.

A more succinct example (wrapped in an undo operation) would be …

mod = Sketchup.active_model
sel = mod.selection
unless sel.empty?
  used_layers = sel.map(&:layer).uniq
  unused_layers = (mod.layers.to_a - used_layers) - [mod.active_layer]
  if !unused_layers.empty?
    mod.start_operation("Hide Unused Tags")
      unused_layers.each {|tag| tag.visible= false }
    mod.commit_operation
  end
end
4 Likes