Link Search Menu Expand Document

If Node

An If Node is an example of a flow control node. It only performs its computation if a special input on the node is true. Otherwise it passes the inputs without modification to its outputs. Note that an if node is implementated as a group node here.

If node base class header.

class COMPUTES_EXPORT IfGroupNodeCompute: public GroupNodeCompute {
  COMPONENT_ID(Compute, IfGroupNodeCompute);
  IfGroupNodeCompute(Entity* entity, ComponentDID did = kDID());
  virtual ~IfGroupNodeCompute();
  // Our state.
  virtual bool update_state();

If node base class implementation.

IfGroupNodeCompute::IfGroupNodeCompute(Entity* entity, ComponentDID did):
    GroupNodeCompute(entity, did) {

IfGroupNodeCompute::~IfGroupNodeCompute() {

bool IfGroupNodeCompute::update_state() {

  // Get the value of the condition.
  QJsonObject in_obj = _inputs->get_main_input_object();
  QJsonValue condition_value = in_obj.value("value");
  bool condition = JSONUtils::convert_to_bool(condition_value);

  // If the "condition" input is false then we copy the value from the main input to the main output.
  // We set the value to zero for all other outputs.
  if (!condition) {
    Entity* outputs = get_entity(Path( { ".", kOutputsFolderName }));
    for (auto &iter : outputs->get_children()) {
      Entity* output_entity = iter.second;
      const std::string& output_name = output_entity->get_name();
      Entity* output_node = our_entity()->get_child(output_name);
      Dep<OutputNodeCompute> output_node_compute = get_dep<OutputNodeCompute>(output_node);
      if (output_name == kMainOutputName) {
        // We copy the value from in to out.
      } else {
        // We set the value to zero for all other outputs.
        set_output(output_name, 0);
  } else {
    // Otherwise we run the normal group compute.
    return GroupNodeCompute::update_state();
  return true;