[advanced ROS chapter] lesson 2 custom header and source file encapsulation

【ROS Advanced 】 The second is Custom header 、 Source file encapsulation

Preface

In the introductory course, we did not do much research on code encapsulation , More about writing cpp File is compiled and used , And want to achieve engineering In the process of ROS System use , You need to use Header file and source file are encapsulated Code , For different packaging methods , Compilation Rules The treatment is not the same , Further analysis is needed .

Custom header file encapsulation

1. technological process

• Concept ： Design your own header file and executable file , And will Executable file In itself As a source file
• technological process ：

1. Write a header file
2. Write executable / As a source file
3. Modify the compilation rule configuration file to compile

2. The header file

• Code demonstration ：

#ifndef _HELLO_H
#define _HELLO_H

namespace hello_ns{
    

class HelloPub {
    

public:
    void run();
};

}

#endif

• Brief analysis ：

1. Macro definition and preprocessing ： Prevent repeated inclusion and compilation of header files

#ifndef _HELLO_H // Test first x Whether defined by macro 
#define _HELLO_H // Procedures section 1 // If x Not defined by macro , Definition x, And compile the program segment  1
...
#endif // End if

2. Namespace ： Prevent conflicts between identifiers , Distinguish between similar functions 、 class 、 Variable

namespace hello_ns{
     
...
}

• c_cpp_properties.json： modify includepath Property to prevent throwing exceptions ;

"/home/ user / working space /src/ Function pack /include/**"

3. Executable file

• Code display ：

#include "ros/ros.h"
#include "test_head/hello.h"

namespace hello_ns {
    

void HelloPub::run(){
    
    ROS_INFO(" Use of custom header file ....");
}

}

int main(int argc, char *argv[])
{
    
    setlocale(LC_ALL,"");
    ros::init(argc,argv,"test_head_node");
    hello_ns::HelloPub helloPub;
    helloPub.run();
    return 0;
}

4. Modify Compilation Rules

• add to include：

include_directories(
include
  ${catkin_INCLUDE_DIRS}
)

• Configuration file dependencies and links ：

add_executable(hello src/hello.cpp)

add_dependencies(hello ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

target_link_libraries(hello
  ${catkin_LIBRARIES}
)

Custom source file encapsulation

1. technological process

• Concept ： Define source files separately 、 The header file 、 Executable file , Include header files in the executable ;
• technological process ：

1. Write a header file ;
2. Write source file ;
3. Write executable ;
4. Write the configuration file and execute ;

2. The header file

• Code display ：head.h

#ifndef _HEAD_H
#define _HEAD_H

namespace hello_ns {
    

class My {
    

public:
    void run();

};

}

#endif

• File directory ： Under the function package include/ Under the function package name （ You also need to configure includepath）

3. Source file

• Code display ：source.cpp

#include "test_head_src/head.h"
#include "ros/ros.h"

namespace hello_ns{
    

void My::run(){
    
    ROS_INFO("hello,head and src ...");
}

}

4. Executable file

• Code display ：use_head.cpp

#include "ros/ros.h"
#include "test_head_src/head.h"

int main(int argc, char *argv[])
{
    
    ros::init(argc,argv,"hahah");
    hello_ns::My my;
    my.run();
    return 0;
}

5. Modify Compilation Rules

• Header file and source file ：

1. include term ：

include_directories(
include
 ${catkin_INCLUDE_DIRS}
)

2. Statement C++ library

add_library(head
 include/test_head_src/head.h
 src/source.cpp
)

3. Dependencies and links

add_dependencies(head >${
     ${
     PROJECT_NAME}_EXPORTED_TARGETS} >${
     catkin_EXPORTED_TARGETS})

target_link_libraries(head
 ${
     catkin_LIBRARIES}
)

• Executable file ：

Dependencies and links ：

add_executable(use_head src/use_head.cpp)

add_dependencies(use_head >${${PROJECT_NAME}_EXPORTED_TARGETS} >${catkin_EXPORTED_TARGETS})

# Here you need to add the previously set  head  library 
target_link_libraries(use_head
 head
 ${catkin_LIBRARIES}
)

summary

• Statement ： The blog section of this section refers to CSDN User zhaoxuzuo ROS course , The next blog will focus on ROS On the operation management of , Introduce the concept of meta function pack and workspace coverage .