   
   func conceptViewFor(concept: Concept) -> ConceptView {
     return conceptViews[concept.identifier]!
+  }
+  
+  func linkViewFor(link: Link) -> LinkView {
+    return linkViews[link.identifier]!
   }
 
   // MARK: - CanvasConceptsActions

    sprint("drag from conceptView \(conceptView.concept.identifier) to \(point)")
    arrowOriginPoint = conceptView.concept.point
    arrowTargetPoint = point
    needsDisplay = true
  }
  

    if let linkView = linkViews[link.identifier] {
      linkView.needsDisplay = true
    } else {
      sprint("draw new link view for \(link)")
      let linkView = LinkView(link: link, canvas: self)
      addSubview(linkView)
      linkViews[link.identifier] = linkView
