t16_global_blackboard.cpp

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#include "behaviortree_cpp/bt_factory.h"
 
using namespace BT;
 
// clang-format off
static const char* xml_main = R"(
<root BTCPP_format="4">
 
  <BehaviorTree ID="MainTree">
    <Sequence>
      <PrintNumber name="main_print" val="{@value}" />
      <SubTree ID="MySub"/>
    </Sequence>
  </BehaviorTree>
 
  <BehaviorTree ID="MySub">
    <Sequence>
      <PrintNumber name="sub_print" val="{@value}" />
      <Script code="@value_sqr := @value * @value" />
    </Sequence>
  </BehaviorTree>
</root>
 )";
 
// clang-format on
 
class PrintNumber : public BT::SyncActionNode
{
public:
  PrintNumber(const std::string& name, const BT::NodeConfig& config)
    : BT::SyncActionNode(name, config)
  {}
 
  NodeStatus tick() override
  {
    const int val = getInput<int>("val").value();
    // If you prefer not having a port and accessing the top-level blackboard
    // directly with an hardcoded address... you should question your own choices!
    // But this is the way it is done
    // val = config().blackboard-><int>("@value");
    std::cout << "[" << name() << "] val: " << val << std::endl;
    return NodeStatus::SUCCESS;
  }
 
  static BT::PortsList providedPorts()
  {
    return { BT::InputPort<int>("val") };
  }
};
 
//---------------------------------------------------
int main()
{
  BehaviorTreeFactory factory;
 
  factory.registerNodeType<PrintNumber>("PrintNumber");
  factory.registerBehaviorTreeFromText(xml_main);
 
  // No one "own" this blackboard
  auto global_blackboard = BT::Blackboard::create();
  // This blackboard will be owned by "MainTree". Its parent is global_blackboard
  auto root_blackboard = BT::Blackboard::create(global_blackboard);
 
  auto tree = factory.createTree("MainTree", root_blackboard);
 
  // we can interact directly with global_blackboard
  for(int i = 1; i <= 3; i++)
  {
    global_blackboard->set("value", i);
    tree.tickOnce();
    int value_sqr = global_blackboard->get<int>("value_sqr");
    std::cout << "[While loop] value: " << i << " value_sqr: " << value_sqr << "\n\n";
  }
 
  return 0;
}
 
/* Expecte output:
 
[main_print] val: 1
[sub_print] val: 1
[While loop] value: 1 value_sqr: 1
 
[main_print] val: 2
[sub_print] val: 2
[While loop] value: 2 value_sqr: 4
 
[main_print] val: 3
[sub_print] val: 3
[While loop] value: 3 value_sqr: 9
 
*/