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Accessing Private Names from a NodeHandle
Description: This tutorial will show you how to access private Names with roscpp's NodeHandle API.Tutorial Level: BEGINNER
Next Tutorial: Using Class Methods as Callbacks
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:
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1 ros::init(argc, argv, "my_node_name");
2 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:
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1 ros::init(argc, argv, "my_node_name");
2 ros::NodeHandle nh1("~"); // must be in main()
3 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:
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1 ros::NodeHandle nh;
2 nh.getParam("~name", ... );
You do this:
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1 ros::NodeHandle nh("~");
2 nh.getParam("name", ... );
Next Tutorial: Using Class Methods as Callbacks
