ros2 自定义消息

在使用ros2时，有时需要自定义一个数据结构传递数据。具体方法如下

## 创建ros2包

ros2 pkg create --build-type ament_cmake --node-name box box

## 创建msg文件夹，并创建*.msg数据结构

cd box
mkdir msg
touch box.msg

box.msg中添加数据结构

std_msgs/Header header
int32 x
int32 y
int32 width
int32 height

## 修改Cmakelist.txt

cmake_minimum_required(VERSION 3.5)
project(box)

# Default to C99
if(NOT CMAKE_C_STANDARD)
  set(CMAKE_C_STANDARD 99)
endif()

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
# uncomment the following section in order to fill in
# further dependencies manually.
# find_package(<dependency> REQUIRED)