Adding SBAtoms to SBGroupNode

[Haichao]

Dear all,

I am trying to create a group of atoms that are distributed on several chains into a one SBNodeGroup.
In the following code I added every atom of my document into a SBNodeGroup, however it doesn't work as I cannot "Select group nodes" in the context menu and groupNodesSize is always zero. Am I missing something here?

 SAMSON::beginHolding("adding myModeGroup");

  SBPointer<SBNodeGroup> nodeGroup = new SBNodeGroup();
  nodeGroup->setName("myNodeGroup");

  SBNodeIndexer allNodes;
  SAMSON::getActiveDocument()->getNodes(allNodes);
  nodeGroup->create();

  SB_FOR(SBNode* node, allNodes) {
    if (node->getType() == SBNode::Atom) {
      nodeGroup->addChild(node);
    }
  }
  
  auto groupNodes = nodeGroup->getGroupNodes();;
  
  int allNodesSize = allNodes.size();
  int groupNodesSize = groupNodes->size();
  
  SAMSON::getActiveDocument()->addChild(nodeGroup());

  SAMSON::endHolding();```

Thank you,
Haichao

[DmitriyMarin]

Hi, @Haichao

You can actually do that using the SBNodeGroup constructor. It may look something like that:

// get an indexer with all the atoms
// you can request specific nodes in the getNodes function itself using the Node Specification Language
SBNodeIndexer nodeIndexer;
SAMSON::getNodes(nodeIndexer, "node.type atom"); 
// or use getNodes function for any SBDataGraphNode you want with a predicate
SAMSON::getActiveDocument()->getNodes(nodeIndexer, SBNode::IsType(SBNode::Atom));

// create a node group based on the nodeIndexer
SBPointer<SBNodeGroup> nodeGroup = new SBNodeGroup("myNodeGroup", nodeIndexer);
nodeGroup->create();

if (nodeGroup->isCreated()) {
  SAMSON::getActiveDocument()->addChild(nodeGroup());
}

[Stephane]

For some context: nodes in a group are not children of the group (a node can only have one parent), but only referenced by the group. As a result , the addChild and removeChild functions are not overloaded in SBNodeGroup, and they have the default behavior: they do nothing. The way to create groups is thus as @Dmitriy-Marin suggested :-).

(This is similar to bonds, which only reference atoms, and are not parents of atoms.)

[Haichao]

Thanks, this solves my problem!