sketchup-delete-layer.rb

=begin

This is how you to delete a Layer prior to SketchUp 2015. 

SketchUp >= 2015 has a Layer.delete method.

(c) TIG 2009
layer-delete.rb adds a new Method the Sketchup's Layer Class- 
"layer.delete()" - it deletes that layer from the model and
entities that used it get the default layer instead...
however, if "layer.delete(true)" then layer's geometry is deleted too.
The default layer cannot be deleted, BUT if 'true' is used anything
on it WILL be deleted - so use it sensibly !

v1.1 simplified defn changing and respond_to? layer testing.
v1.2 operation removed.
v1.3 empty temp groups used for layers without detriment.
v1.4 deletes layer's geometry with (delete_geometry)==true.

=end
require 'sketchup.rb'

module YOU

  def delete_layer(delete_geometry = false)
    model=Sketchup.active_model
    ents=model.entities; defs=model.definitions; layers=model.layers
    if delete_geometry
      allents=[]
      ents.each{|e|allents << e if e.valid? and e.respond_to?(:layer) and e.layer==self}
      defs.each{|d|d.entities.each{|e| allents << e if e.valid? and e.respond_to?(:layer)and e.layer == self}}
      allents.each{|e|e.erase! if e.valid?}
    else # move geom to Layer0 etc
      ents.each{|e|e.layer=nil if e.respond_to?(:layer) and e.layer==self}
      defs.each{|d|d.entities.each{|e|e.layer = nil if e.respond_to?(:layer) and e.layer == self}}
    end #if
    group=ents.add_group();gents=group.entities ### temporarily use other layers
    temp = gents.add_group()
    temp.layer = nil
    (layers.to_a-[self]).each{|layer| tc = temp.copy; tc.layer=layer}
    model.active_layer = nil if model.active_layer == self # ensure self is not current layer
    layers.purge_unused ### purge self from browser
    group.erase! ### erase! the temporary layer user, use set as was.
  end #def

end # module