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Update the documentation
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‎docs/tutorial_B_node_parameters.md

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NodeParameters are like arguments passed to a function.
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They are a map of __key/value__ pairs (both strings) that are usually
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parsed from file.
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read from file.
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To create a TreeNodes that accepts NodeParameters, you must follow these rules:
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- Use inheritance. NodeParameters are __not supported__ by *SimpleActionNodes* nor
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*SimpleConditionNodes*.
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- Inherit from either ActionNodeBase, ActionNode, ConditionNode or DecoratorNode.
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- You must provide a constructor with the following signature:
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static const BT::NodeParameters& requiredNodeParameters()
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```
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Alternatively, since version 2.2, Simple Nodes can also support NodeParameters.
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Check the [tutorial 6](tutorial_G_legacy.md) for details.
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## Example: an Action requiring the parameter "message"
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‎docs/tutorial_G_legacy.md

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# Wrap legacy code
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In this tutorial we see how to deal with legacy code that was not meant to be used
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with BehaviorTree.CPP.
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Let's start supposing that this is my class.
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``` c++
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// This is my custom type.
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struct Point3D { double x,y,z; };
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class MyLegacyMoveTo
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{
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public:
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bool go(Point3D goal)
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{
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printf("Going to: %f %f %f\n", goal.x, goal.y, goal.z);
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return true; // true means success in my legacy code
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}
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};
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```
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We want to create an ActionNode called "MoveTo" that invokes the method __MyLegacyMoveTo::go()__.
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The final goal is to be able to use this ActionNode in a tree like this one:
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``` XML
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<root main_tree_to_execute = "MainTree" >
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<BehaviorTree ID="MainTree">
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<SequenceStar name="root">
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<MoveTo goal="-1;3;0.5" />
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<MoveTo goal="${myGoal}" />
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</SequenceStar>
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</BehaviorTree>
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</root>
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```
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The first thing that we need to do is to allow our library to convert
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a NodeParameter (that is
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nothing more than a pair of strings representing key/value) into a Point3D.
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As we did in a previous tutorial, we should implement a template specialization
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for __convertFromString__.
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Our particular string representation of a Point3D consists in three semicolon-separated
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numbers, representing __x, y and z_.
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``` c++
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namespace BT
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{
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template <> Point3D convertFromString(const StringView& key)
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{
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// three real numbers separated by semicolons
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auto parts = BT::splitString(key, ';');
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if (parts.size() != 3)
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{
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throw std::runtime_error("invalid input)");
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}
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else
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{
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Point3D output;
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output.x = convertFromString<double>(parts[0]);
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output.y = convertFromString<double>(parts[1]);
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output.z = convertFromString<double>(parts[2]);
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return output;
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}
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}
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}
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```
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Finally, we can use a __C++11 lambda__ (or, alternatively, __std::bind__) to wrap
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out method into a function with the right signature.
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``` c++
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int main()
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{
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using namespace BT;
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MyLegacyMoveTo move_to;
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// Here we use a lambda that captures the reference of move_to
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auto MoveToWrapperWithLambda = [&move_to](TreeNode& parent_node) -> NodeStatus
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{
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Point3D goal;
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// thanks to paren_node, you can access easily the NodeParameters and the blackboard
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parent_node.getParam("goal", goal);
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bool res = move_to.go( goal );
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// convert bool to NodeStatus
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return res ? NodeStatus::SUCCESS : NodeStatus::FAILURE;
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};
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BehaviorTreeFactory factory;
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factory.registerSimpleAction("MoveTo", MoveToWrapperWithLambda);
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auto blackboard = Blackboard::create<BlackboardLocal>();
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auto tree = buildTreeFromText(factory, xml_text, blackboard);
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// We set the entry "myGoal" in the blackboard.
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Point3D my_goal = {3,4,5};
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blackboard->set("myGoal", my_goal);
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NodeStatus status = NodeStatus::RUNNING;
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while (status == NodeStatus::RUNNING)
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{
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status = tree.root_node->executeTick();
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}
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return 0;
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}
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/* Expected output:
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Going to: -1.000000 3.000000 0.500000
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Going to: 3.000000 4.000000 5.000000
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The first MoveTo read the parameter from the string "-1;3;0.5"
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whilst the second from the blackboard, that contains a copy of the Point3D my_goal.
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*/
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```
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The functor we are passing to __SimpleActionNode__ requires the following signature:
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BT::NodeStatus myFunction(BT::TreeNode& parent)
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As a consequence, we can access a NodeParameter by
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parent.getParam()
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or even set/get an entry of the Blackboard using
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parent.blackboard()
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‎examples/t06_wrap_legacy.cpp

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};
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// Similarly to the previous tutorials, we need to implement this parsing method,
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// deplaring a specialization of BT::convertFromString
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// providing a specialization of BT::convertFromString
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namespace BT
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{
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template <> Point3D convertFromString(const StringView& key)
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};
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BehaviorTreeFactory factory;
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// Regoister the lambda with BehaviorTreeFactory::registerSimpleAction
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// Register the lambda with BehaviorTreeFactory::registerSimpleAction
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factory.registerSimpleAction("MoveTo", MoveToWrapperWithLambda);
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auto blackboard = Blackboard::create<BlackboardLocal>();

‎mkdocs.yml

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feature:
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tabs: true
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palette:
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primary: blue
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accent: indigo
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primary: blue grey
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accent: green
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font:
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text: Ubuntu
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code: Roboto Mono
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- "Tutorial 4: Subtrees": tutorial_D_subtrees.md
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- "Tutorial 5: Plugins": tutorial_E_plugins.md
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- "Tutorial 6: Loggers": tutorial_F_loggers.md
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- "Tutorial 7: Legacy code": tutorial_G_legacy.md
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