 
 
 ApparatusViewer.Attribute = class Attribute
-  constructor: (@_attribute) ->
+  constructor: (@_attribute, @_viewer) ->
 
   # Returns the current value of the attribute.
   value: ->

      throw "Found no attributes with label #{label}"
    if foundMultiple
      throw "Found multiple attributes with label #{label}"
    return new Attribute(attribute)

  # ADVANCED USAGE: Returns a reference to the internal `Project` object being
  # displayed in the viewer. You can read and write to this object, but beware:

  # Sets the defining expression of the attribute to the string given.
  setExpression: (exprString) ->
    @_attribute.setExpression(exprString)
    @_viewer._refresh()
    return

  # ADVANCED USAGE: Returns a reference to the internal `Attribute` node
