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## descriptive title for the tutorial
## title = Accessing Private Names from a NodeHandle
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## description = This tutorial will show you how to access private [[Names]] with roscpp's `NodeHandle` API.
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== Why not just ~name? ==
The introduction of `NodeHandles` in roscpp created something of a conundrum when dealing with private names.  If I create a `NodeHandle` with its own namespace:
{{{#!cplusplus
ros::init(argc, argv, "my_node_name");
ros::NodeHandle nh("/my_node_handle_namespace");
}}}

Where should a private name resolve?  Some options would be:
 * `/my_node_handle_namespace/my_node_name/name`
 * `my_node_name/my_node_handle_namespace/name`
 * `/my_node_handle_namespace/name`
 * Something else entirely

For this reason, `NodeHandle` does not allow passing private names directly to its methods, or to constructors that take a `NodeHandle` as an argument.

== Accessing Private Names ==
The solution is to construct a `NodeHandle` with a private name as its namespace:
{{{#!cplusplus
ros::init(argc, argv, "my_node_name");
ros::NodeHandle nh1("~");  // must be in main()
ros::NodeHandle nh2("~foo");
}}}

`nh1`'s namespace is `/my_node_name`, and `nh2`'s namespace is `/my_node_name/foo`.

So instead of doing this:
{{{#!cplusplus
ros::NodeHandle nh;
nh.getParam("~name", ... );
}}}

You do this:
{{{#!cplusplus
ros::NodeHandle nh("~");
nh.getParam("name", ... );
}}}

'''Next Tutorial''': [[roscpp_tutorials/Tutorials/UsingClassMethodsAsCallbacks|Using Class Methods as Callbacks]]

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