I have a trouble in the code,and need help.thanks!

[winzard]

require'sketchup.rb'
class Model
   def create_model
      UI.messagebox('The number of the building less than 6!')
     prompts=["length of land","width of land","The number of building","building length","building width","building height","Spacing"]
     input=UI.inputbox prompts,"Create model"
     lengthl,widthl,number,blength,bwidth,bheight,spacing=input
     amount=0
     model=Sketchup.active_model
     entities=model.entities
     if(amount>6)
         then UI.messagebox('The number of the building more than 6!')
     pt1=[0,0,0]
     pt2=[0+bwidth,0,0]
     pt3=[0+blength,0+bwidth,0]
     pt4=[0,0+blength,0]
     new_face=entities.add_face pt1,pt2,pt3,pt4
     new_face.pushupull bheight
   end
end
UI.menu("Plugins").add_item("creat_model"){
object=Model.new()
object.create_model
}

I want to Creat Geometry by the code,but I can't find out where the error.

[TIG]

I wouldn't mess with the Model class... make it a simple tool... Here's a reworked version... ### marks changes - several small errors and a typo !!!

require 'sketchup.rb'
def create_model()###
  ###UI.messagebox('The number of the building less than 6!') ### why here ?
  ### set up some starting defaults - change as you want...
  @lengthl=100.m if not @length1
  @widthl=50.m if not @widthl
  @number=4 if not @number
  @blength=10.m if not @blength
  @bwidth=5.m if not @bwidth
  @bheight=5.m if not @bheight
  @spacing=5.m if not @spacing
  prompts=["Length of Land; ","Width of Land; ","The Number of Building; ","Building Length; ","Building Width; ","Building Height; ","Building Spacing; "]###
  defaults=[@lengthl,@widthl,@number,@blength,@bwidth,@bheight,@spacing]
  input=UI.inputbox(prompts,defaults,[],"Create Model") ### note extra items
  return nil if not input ###
  @lengthl,@widthl,@number,@blength,@bwidth,@bheight,@spacing=input ###
  amount=@number ### ???
  model=Sketchup.active_model
  entities=model.active_entities ###
  if amount>6
    UI.messagebox('The number of building is more than 6 !')### why ???
  else
    model.start_operation("Create Model")### for the 'undo'
     x=0;y=0 ### also don't muddle the width/height !!!
     amount.times{|i|
       pt1=[x,y,0]###
       pt2=[x+@bwidth,y,0]###
       pt3=[x+@bwidth,y+@blength,0]###
       pt4=[x,y+@blength,0]###
       new_face=entities.add_face(pt1,pt2,pt3,pt4)
       new_face.pushpull(-@bheight)
       ### pushUpull typo !!! -ve = pull up as the face is reversed...
       x=x+@bwidth+@spacing ### set in a line
       ### you can mess on with x & y spacings and number of buildings etc...
       ### presumably you'll also use the 'Land' sizes somewhere ?
      } ###
    model.commit_operation ###
  end#if ###
end#def ###
if not file_loaded?(File.basename(__FILE__)) ### so only get menu item once...
    UI.menu("Plugins").add_item("Create Model"){create_model} ###
end#if ###
file_loaded(File.basename(__FILE__)) ###

[winzard]

Thank you very much!It is greate help to me!