Wraping legacy code

如何处理不打算在BehaviorTree.CPP中使用的旧代码；

类可能是如下：

// This is my custom type.
struct Point3D { double x,y,z; };

// We want to create an ActionNode to calls method MyLegacyMoveTo::go
class MyLegacyMoveTo
{
public:
    bool go(Point3D goal)
    {
        printf("Going to: %f %f %f\n", goal.x, goal.y, goal.z);
        return true; // true means success in my legacy code
    }
};

需要去实现convertFromString.

namespace BT
{
    template <> Point3D convertFromString(StringView key)
    {
        // three real numbers separated by semicolons
        auto parts = BT::splitString(key, ';');
        if (parts.size() != 3)
        {
            throw RuntimeError("invalid input)");
        }
        else{
            Point3D output;
            output.x  = convertFromString<double>(parts[0]);
            output.y  = convertFromString<double>(parts[1]);
            output.z  = convertFromString<double>(parts[2]);
            return output;
        }
    }
} // end anmespace BT

为了去封装方法MyLegacyMoveTo::go，需要一个lambda或者std::bind函数去创建一个指针以及一个SimpleActionNode；

static const char* xml_text = R"(

 <root>
     <BehaviorTree>
        <MoveTo  goal="-1;3;0.5" />
     </BehaviorTree>
 </root>
 )";

int main()
{
    using namespace BT;

    MyLegacyMoveTo move_to;

    // Here we use a lambda that captures the reference of move_to
    auto MoveToWrapperWithLambda = [&move_to](TreeNode& parent_node) -> NodeStatus
    {
        Point3D goal;
        // thanks to paren_node, you can access easily the input and output ports.
        parent_node.getInput("goal", goal);

        bool res = move_to.go( goal );
        // convert bool to NodeStatus
        return res ? NodeStatus::SUCCESS : NodeStatus::FAILURE;
    };

    BehaviorTreeFactory factory;

    // Register the lambda with BehaviorTreeFactory::registerSimpleAction

    PortsList ports = { BT::InputPort<Point3D>("goal") };
    factory.registerSimpleAction("MoveTo", MoveToWrapperWithLambda, ports );

    auto tree = factory.createTreeFromText(xml_text);

    tree.tickRoot();

    return 0;
}

/* Expected output:

Going to: -1.000000 3.000000 0.500000

*/