Difference between revisions of "Documentation/Nightly/Developers/MRML/NodeReferences"

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== API Description ==
 
== API Description ==
  
The node reference API automatically takes care of (1) read/write/copy of
+
The node reference API automatically takes care of
node references, (2) updating references on scene import, (3) adding and deleting
+
(1) read/write/copy of node references,
nodes. All that functionality is implemented in the <code>vtkMRMLNode</code> base
+
(2) updating references on scene import,
class. The only thing that needs to happen in the derived MRML node class
+
(3) adding and deleting nodes.
(usually in the constructor of the class)
+
 
is a call to <code>vtkMRMLNode::AddNodeReferenceRole(const char *referenceRole,
+
All that functionality is implemented in the [{{doxygen-class-url|vtkMRMLNode}} vtkMRMLNode] base class.  
const char *mrmlAttributeName)</code>
+
 
that takes a unique string defining the reference role between this node
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The only thing that needs to happen in the derived MRML node class (usually in the constructor of the class)
 +
is a call to <code>vtkMRMLNode::AddNodeReferenceRole(const char *referenceRole, const char *mrmlAttributeName)</code>
 +
that takes a unique string defining the reference role between this node  
 
and the referenced node, and a MRML attribute name for storing the
 
and the referenced node, and a MRML attribute name for storing the
 
reference in the .mrml file.
 
reference in the .mrml file.
Line 28: Line 30:
 
vtkMRMLNode* AddAndObserveNodeReferenceID(const char* referenceRole , const char* referencedNodeID, vtkIntArray *events=0);
 
vtkMRMLNode* AddAndObserveNodeReferenceID(const char* referenceRole , const char* referencedNodeID, vtkIntArray *events=0);
 
</pre>
 
</pre>
if the multiple instances of this reference are allowed.
+
if multiple instances of this reference are allowed.
  
vtkMRMLNode also provides virtual callbacks that can be extended in the
+
[{{doxygen-class-url|vtkMRMLNode}} vtkMRMLNode] also provides virtual callbacks that can be extended in the
 
derived classes:
 
derived classes:
* OnNodeReferenceAdded(vtkMRMLNodeReference *reference)
+
<pre>
* OnNodeReferenceRemoved(vtkMRMLNodeReference *reference)
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OnNodeReferenceAdded(vtkMRMLNodeReference *reference)
* OnNodeReferenceModified(vtkMRMLNodeReference *reference)
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OnNodeReferenceRemoved(vtkMRMLNodeReference *reference)
 +
OnNodeReferenceModified(vtkMRMLNodeReference *reference)
 +
</pre>
  
 
By default those methods generate the following events:
 
By default those methods generate the following events:
* vtkMRMLNode::ReferenceAddedEvent
+
<pre>
* vtkMRMLNode::ReferenceRemovedEvent
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vtkMRMLNode::ReferenceAddedEvent
* vtkMRMLNode::ReferenceModifiedEvent
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vtkMRMLNode::ReferenceRemovedEvent
 +
vtkMRMLNode::ReferenceModifiedEvent
 +
</pre>
  
 
In the derived classes those methods could be extended using <code>vtkMRMLNode</code>
 
In the derived classes those methods could be extended using <code>vtkMRMLNode</code>

Revision as of 22:10, 3 April 2015

Home < Documentation < Nightly < Developers < MRML < NodeReferences


For the latest Slicer documentation, visit the read-the-docs.


Overview

This page explains how to create a MRML node that reference and observes other MRML nodes.

As describe in the MRML Nodes section, node references allow to associate data node implementing interfaces (like Displayable, Storable and Transformable) with a representation node (like Storage or Display node) or other data node (like Transform node).

API Description

The node reference API automatically takes care of (1) read/write/copy of node references, (2) updating references on scene import, (3) adding and deleting nodes.

All that functionality is implemented in the vtkMRMLNode base class.

The only thing that needs to happen in the derived MRML node class (usually in the constructor of the class) is a call to vtkMRMLNode::AddNodeReferenceRole(const char *referenceRole, const char *mrmlAttributeName) that takes a unique string defining the reference role between this node and the referenced node, and a MRML attribute name for storing the reference in the .mrml file.

The only other call that is needed is either:

vtkMRMLNode* SetAndObserveNodeReferenceID(const char* referenceRole , const char* referencedNodeID, vtkIntArray *events=0);

or

vtkMRMLNode* AddAndObserveNodeReferenceID(const char* referenceRole , const char* referencedNodeID, vtkIntArray *events=0);

if multiple instances of this reference are allowed.

vtkMRMLNode also provides virtual callbacks that can be extended in the derived classes:

OnNodeReferenceAdded(vtkMRMLNodeReference *reference)
OnNodeReferenceRemoved(vtkMRMLNodeReference *reference)
OnNodeReferenceModified(vtkMRMLNodeReference *reference)

By default those methods generate the following events:

vtkMRMLNode::ReferenceAddedEvent
vtkMRMLNode::ReferenceRemovedEvent
vtkMRMLNode::ReferenceModifiedEvent

In the derived classes those methods could be extended using vtkMRMLNode API that allows querying of node's references:

  • char *GetNthNodeReferenceID(const char* referenceRole, int n);
  • vtkMRMLNode* GetNthNodeReference(const char* referenceRole, int n);
  • int GetNumberOfNodeReferences(const char* referenceRole);
  • etc.

For full API see: http://slicer.org/doc/html/classvtkMRMLNode-members.html

Currently the following MRML nodes are implemented using MRML Node Reference API:

Other references to MRML nodes such as to vtkMRMLColorTableNode, vtkMRMLDiffusionTensorDisplayPropertiesNode are currently not using this API.

Module parameter nodes that contain references to input/output Volume/Model, etc. nodes may or may not require a new API since not all of them contain logic to deal with reference changes.

Examples

  • vtkMRMLTransformableNode implementation:

http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Libs/MRML/Core/vtkMRMLTransformableNode.h?view=log

  • vtkMRMLDisplayableNodeimplementation:

http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Libs/MRML/Core/vtkMRMLDisplayableNode.h?view=log

  • vtkMRMLStorableNodeimplementation:

http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Libs/MRML/Core/vtkMRMLStorableNode.h?view=log

History

In Slicer4.2 prior to March of 2013 each MRML node that contained references to other MRML nodes (for example each vtkMRMLDisplayableNode contained a reference to an instance vtkMRMLDisplayNode) was responsible for managing the references internally. This involved complicated logic and bookkeeping to maintain the references in sync when importing scenes, adding/deleting nodes, modifying referenced nodes, etc.

When creating a new node with the reference to another node the following methods needed to be created/updated to handle the references:


  • Copy
  • PrintSelf
  • ReadXMLAttributes
  • WriteXML
  • ProcessMRMLEvents
  • UpdateReferenceID
  • SetSceneReferences
  • UpdateScene
  • UpdateReferences
  • SetAndObserveNodeReferenceID