Use tf prefix properly (backport #688) (#725)

Remove tf_prefix workaround in hw interface

ros2_control can now accept empty parameters, so this isn't needed anymore.

Co-authored-by: Lennart Nachtigall <[email protected]>

Author: mergify[bot]

ur_robot_driver/src/hardware_interface.cpp

@@ -164,8 +164,7 @@ std::vector<hardware_interface::StateInterface> URPositionHardwareInterface::exp
   // Obtain the tf_prefix from the urdf so that we can have the general interface multiple times
   // NOTE using the tf_prefix at this point is some kind of workaround. One should actually go through the list of gpio
   // state interface in info_ and match them accordingly
-  std::string tf_prefix = info_.hardware_parameters.at("tf_prefix");
-  tf_prefix.erase(0, 1);
+  const std::string tf_prefix = info_.hardware_parameters.at("tf_prefix");
   state_interfaces.emplace_back(hardware_interface::StateInterface(tf_prefix + "speed_scaling", "speed_scaling_factor",
                                                                    &speed_scaling_combined_));
 
@@ -248,8 +247,8 @@ std::vector<hardware_interface::CommandInterface> URPositionHardwareInterface::e
   // Obtain the tf_prefix from the urdf so that we can have the general interface multiple times
   // NOTE using the tf_prefix at this point is some kind of workaround. One should actually go through the list of gpio
   // command interface in info_ and match them accordingly
-  std::string tf_prefix = info_.hardware_parameters.at("tf_prefix");
-  tf_prefix.erase(0, 1);
+  const std::string tf_prefix = info_.hardware_parameters.at("tf_prefix");
+
   command_interfaces.emplace_back(
       hardware_interface::CommandInterface(tf_prefix + "gpio", "io_async_success", &io_async_success_));