Pass additional arguments during initialization and/or construction

目的是为了扩展之前的写法，如

    MyCustomNode(const std::string& name, const NodeConfiguration& config);

如果需要在构造函数中，添加额外的参数

不建议使用黑板的形式：

理论上可以使用黑板中的输入端口来实现，但是错误情况如下：

参数在编译之前就知道(deployment-time.)；

参数在运行时不能改变；

参数不需要从XML中来设置；

方法1：注册一个自定义的builder

下面自定义的节点成为Action_A:

打算传递三个附加的参数：可以是任意复杂的对象，不仅限于内建对象：

// Action_A has a different constructor than the default one.
class Action_A: public SyncActionNode
{

public:
    // additional arguments passed to the constructor
    Action_A(const std::string& name, const NodeConfiguration& config,
             int arg1, double arg2, std::string arg3 ):
        SyncActionNode(name, config),
        _arg1(arg1),
        _arg2(arg2),
        _arg3(arg3) {}

    // this example doesn't require any port
    static PortsList providedPorts() { return {}; }

    // tick() can access the private members
    NodeStatus tick() override;

private:
    int _arg1;
    double _arg2;
    std::string _arg3;
};

本节点通过如下注册：

BehaviorTreeFactory factory;

// A node builder is a functor that creates a std::unique_ptr<TreeNode>.
// Using lambdas or std::bind, we can easily "inject" additional arguments.
NodeBuilder builder_A =
   [](const std::string& name, const NodeConfiguration& config)
{
    return std::make_unique<Action_A>( name, config, 42, 3.14, "hello world" );
};

// BehaviorTreeFactory::registerBuilder is a more general way to
// register a custom node.
factory.registerBuilder<Action_A>( "Action_A", builder_A);

// Register more custom nodes, if needed.
// ....

// The rest of your code, where you create and tick the tree, goes here.
// ....

方法二：使用初始init函数

在tick树之前，使用init方法：

class Action_B: public SyncActionNode
{

public:
    // The constructor looks as usual.
    Action_B(const std::string& name, const NodeConfiguration& config):
        SyncActionNode(name, config) {}

    // We want this method to be called ONCE and BEFORE the first tick()
    void init( int arg1, double arg2, const std::string& arg3 )
    {
        _arg1 = (arg1);
        _arg2 = (arg2);
        _arg3 = (arg3);
    }

    // this example doesn't require any port
    static PortsList providedPorts() { return {}; }

    // tick() can access the private members
    NodeStatus tick() override;

private:
    int _arg1;
    double _arg2;
    std::string _arg3;
};

注册和初始化Action_B有点不同：

BehaviorTreeFactory factory;

// The regitration of  Action_B is done as usual, but remember
// that we still need to call Action_B::init()
factory.registerNodeType<Action_B>( "Action_B" );

// Register more custom nodes, if needed.
// ....

// Create the whole tree
auto tree = factory.createTreeFromText(xml_text);

// Iterate through all the nodes and call init() if it is an Action_B
for( auto& node: tree.nodes )
{
    // Not a typo: it is "=", not "=="
    if( auto action_B = dynamic_cast<Action_B*>( node.get() ))
    {
        action_B->init( 42, 3.14, "hello world");
    }
}

// The rest of your code, where you tick the tree, goes here.
// ....