t03_generic_ports.cpp

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#include "behaviortree_cpp/bt_factory.h"
 
using namespace BT;
 
/* This tutorial will teach you how to deal with ports when its
 *  type is not std::string.
*/
 
// We want to be able to use this custom type
struct Position2D
{
  double x, y;
};
 
// It is recommended (or, in some cases, mandatory) to define a template
// specialization of convertFromString that converts a string to Position2D.
namespace BT
{
template <>
inline Position2D convertFromString(StringView str)
{
  printf("Converting string: \"%s\"\n", str.data());
 
  // real numbers separated by semicolons
  auto parts = splitString(str, ';');
  if(parts.size() != 2)
  {
    throw RuntimeError("invalid input)");
  }
  else
  {
    Position2D output;
    output.x = convertFromString<double>(parts[0]);
    output.y = convertFromString<double>(parts[1]);
    return output;
  }
}
}  // end namespace BT
 
class CalculateGoal : public SyncActionNode
{
public:
  CalculateGoal(const std::string& name, const NodeConfig& config)
    : SyncActionNode(name, config)
  {}
 
  NodeStatus tick() override
  {
    Position2D mygoal = { 1.1, 2.3 };
    setOutput("goal", mygoal);
    return NodeStatus::SUCCESS;
  }
  static PortsList providedPorts()
  {
    return { OutputPort<Position2D>("goal") };
  }
};
 
class PrintTarget : public SyncActionNode
{
public:
  PrintTarget(const std::string& name, const NodeConfig& config)
    : SyncActionNode(name, config)
  {}
 
  NodeStatus tick() override
  {
    auto res = getInput<Position2D>("target");
    if(!res)
    {
      throw RuntimeError("error reading port [target]:", res.error());
    }
    Position2D goal = res.value();
    printf("Target positions: [ %.1f, %.1f ]\n", goal.x, goal.y);
    return NodeStatus::SUCCESS;
  }
 
  static PortsList providedPorts()
  {
    // Optionally, a port can have a human readable description
    const char* description = "Simply print the target on console...";
    return { InputPort<Position2D>("target", description) };
  }
};
 
//----------------------------------------------------------------
 
// clang-format off
static const char* xml_text = R"(
 
 <root BTCPP_format="4" >
     <BehaviorTree ID="MainTree">
        <Sequence name="root">
            <CalculateGoal   goal="{GoalPosition}" />
            <PrintTarget     target="{GoalPosition}" />
            <Script          code="OtherGoal='-1;3'" />
            <PrintTarget     target="{OtherGoal}" />
        </Sequence>
     </BehaviorTree>
 </root>
 )";
 
// clang-format on
 
int main()
{
  using namespace BT;
 
  BehaviorTreeFactory factory;
  factory.registerNodeType<CalculateGoal>("CalculateGoal");
  factory.registerNodeType<PrintTarget>("PrintTarget");
 
  auto tree = factory.createTreeFromText(xml_text);
 
  tree.tickWhileRunning();
 
  /* Expected output:
 *
    Target positions: [ 1.1, 2.3 ]
    Converting string: "-1;3"
    Target positions: [ -1.0, 3.0 ]
*/
  return 0;
}