ROS_hydro_catkin建立标准程序包_helloworld.h+helloworld.cpp+helloworldnode.cpp

1.创建标准catkin工作空间

mkdir mycatkin

cd mycatkin

mkdir build devel src

catkin_make

source devel/setup.bash

2.创建一个catkin程序包

mkdir src/modular_lib_pkg

Add bare-bones Catkin

CMakeLists.txt

and

package.xml

files to make yourdirectory a valid package:

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibility
cmake_minimum_required(VERSION 2.8)

# Declare the name of the CMake Project
project(modular_lib_pkg)

# Find Catkin
find_package(catkin REQUIRED)
# Declare this project as a catkin package
catkin_package()

src/modular_lib_pkg/package.xml

<package>
<!-- Package Metadata -->
<name>modular_lib_pkg</name>
<maintainer email="you@example.com">Your Name</maintainer>
<description>
A ROS tutorial on modularity.
</description>
<version>0.0.0</version>
<license>BSD</license>

<!-- Required by Catkin -->
<buildtool_depend>catkin</buildtool_depend>
</package>

3.Separating Functionality into a Library

Create the Library Code

The header with the declaration of our

say_hello()

function is as follows:

modular_lib_pkg/include/modular_lib_pkg/hello_world.h

// Inclusion guard to prevent this header from being included multiple times
#ifndef __MODULAR_LIB_PKG_HELLO_WORLD_H
#define __MODULAR_LIB_PKG_HELLO_WORLD_H

//! Broadcast a hello-world message over ROS_INFO
void say_hello();

#endif

The source file with the definition of

say_hello()

is as follows:

modular_lib_pkg/src/hello_world.cpp

// Include the ROS C++ APIs
#include <ros/ros.h>

void say_hello() {
ROS_INFO_STREAM("Hello, world!");
}

Now that we’ve written the code for the library, we can add a rule to the

CMakeLists.txt

file to actually build it. Note that just like in the ROS C++hello-world tutorial9,
we need to add a dependency on

roscpp

in order to use ROS. This is just like adding an executable with the

add_executable()

CMake command: instead, we use

add_library()

:

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibility
cmake_minimum_required(VERSION 2.8)

# Declare the name of the CMake Project
project(modular_lib_pkg)

# Find and get all the information about the roscpp package
find_package(roscpp REQUIRED)

# Find Catkin
find_package(catkin REQUIRED)
# Declare this project as a catkin package
catkin_package()

# Add the headers from roscpp
include_directories(${roscpp_INCLUDE_DIRS})

# Define a library target called hello_world
add_library(hello_world src/hello_world.cpp)
target_link_libraries(hello_world ${roscpp_LIBRARIES})

Also, now that we’re using the

roscpp

package, we need to list itas a build- and run-dependency of our package:

src/modular_lib_pkg/package.xml

<package>
<!-- Package Metadata -->
<name>modular_lib_pkg</name>
<maintainer email="you@example.com">Your Name</maintainer>
<description>
A ROS tutorial on modularity.
</description>
<version>0.0.0</version>
<license>BSD</license>

<!-- Required by Catkin -->
<buildtool_depend>catkin</buildtool_depend>

<!-- Package Dependencies -->
<build_depend>roscpp</build_depend>
<run_depend>roscpp</run_depend>
</package>

cd mycatkin

catkin_make

4.建立节点

modular_lib_pkg/src/hello_world_node.cpp

// Include the ROS C++ APIs
#include <ros/ros.h>

// Include the declaration of our library function
#include <modular_lib_pkg/hello_world.h>

// Standard C++ entry point
int main(int argc, char** argv) {
// Initialize ROS
ros::init(argc, argv, "hello_world_node");
ros::NodeHandle nh;

// Call our library function
say_hello();

// Wait for SIGINT/Ctrl-C
ros::spin();
return 0;
}

To build this node, just add an appropriate

add_executable()

call to thebottom of the package’s

CMakeLists.txt

:

add_executable(hello_world_node src/hello_world_node.cpp)
target_link_libraries(hello_world_node ${roscpp_LIBRARIES})

5.编译节点

At this point, you can try to build

hello_world_node

with

catkin_make

, but youwill see the following error:

[100%] Building CXX object modular_lib_pkg/CMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.o
/tmp/src/modular_lib_pkg/src/hello_world_node.cpp:5:42: fatal error: modular_lib_pkg/hello_world.h: No such file or directory
compilation terminated.

The compiler is complaining about

modular_lib_pkg/hello_world.h

notexisting, but weknow it exists! The problem isn’t that the file doesn’texist, but rather that we haven’t told the compiler where to look for it.

In the same way that we added the header search paths for

roscpp

, we alsoneed to add our own local include directory where we put our own headers. To doso, just add the relative path to

src/modular_lib_pkg/include

to theexisting

include_directories()

command in

CMakeLists.txt

:

include_directories(include ${roscpp_INCLUDE_DIRS)

Building the Node (and getting a linker error)

At this point, you can try to build

hello_world_node

with

catkin_make

again, but you will see another error:

[100%] Building CXX object modular_lib_pkg/CMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.o
Linking CXX executable /tmp/foo/devel/lib/modular_lib_pkg/hello_world_node
CMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.o:hello_world_node.cpp:function main: error: undefined reference to 'say_hello()'
collect2: ld returned 1 exit status

This time,

hello_world_node.cpp

is compiled successfully, but thelinkerreports an error that the

say_hello()

function is undefined. The declarationwas found in the

hello_world.h

header file, otherwise
it wouldn’t havecompiled, still the definition from

hello_world.cpp

was missing.

In order to resolve this, in addition to linking against

${roscpp_LIBRARIES}

,we also link

hello_world_node

against the

hello_world

target so that itssymbols are defined for the linker. This is done by adding

hello_world

to theexisting

target_link_libraries()

command like the following:

target_link_libraries(hello_world_node ${roscpp_LIBRARIES} hello_world)

The following

CMakeLists.txt

file contains both this and the previousmodifications:

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibility
cmake_minimum_required(VERSION 2.8)

# Declare the name of the CMake Project
project(modular_lib_pkg)

# Find and get all the information about the roscpp package
find_package(roscpp REQUIRED)

# Find Catkin
find_package(catkin REQUIRED)
# Declare this project as a catkin package
catkin_package()

# Add the local headers and the headers from roscpp
include_directories(include ${roscpp_INCLUDE_DIRS})

# Define a library target called hello_world
add_library(hello_world src/hello_world.cpp)
target_link_libraries(hello_world ${roscpp_LIBRARIES})

# Define an executable target called hello_world_node
add_executable(hello_world_node src/hello_world_node.cpp)
target_link_libraries(hello_world_node ${roscpp_LIBRARIES} hello_world)

catkin_make

rosrun modular_lib_pkg hello_world_node

问题：

[rosrun] Couldn't find executable named hello_world_node below /home/hsn/mycatkin/src/modular_lib_pkg

解决：

cd mycatkin

source devel/setup.bash

其他问题：

roscore

或者sudo apt-get update

参考：http://jbohren.com/articles/modular-ros-packages/