1 The data type of the interface

type name C++ Python DDS type
bool bool bool boolean
byte uint8_t bytes octet
char char str char
float32 float float float
float64 double float double
int8 int8_t int octet
uint8 uint8_t int octet
int16 int16_t int short
uint16 uint16_t int unsigned short
int32 int32_t int long
uint32 uint32_t int unsigned long
int64 int64_t int long long
uint64 uint64_t int unsigned long long
string std::string str string
wstring std::u16string str wstring

1.1 Naming rules

1.Field names must be lowercase alphanumeric characters with underscores to separate words. 2.Field names must start with an alphabetic character, cannot end with an underscore, and can never have two consecutive underscores.

1.2 Set default values

uint8 x 42
int16 y -2000
string full_name "John Doe"
int32[] samples [-200, -100, 0, 100, 200]

1.3 Setting constants

int32 X=123
int32 Y=-123
string FOO="foo"
string EXAMPLE='bar'

2 Create an interface package

ros2 pkg create --build-type ament_cmake tutorial_interfaces

3 Create an interface directory

mkdir msg
mkdir srv
mkdir action

4 Define the interface

4.1 Num.msg file in the msg directory

int num

4.2 AddThreeInts.srv file in the srv directory

int64 a
int64 b
int64 c
int64 sum

4.3 The Fibonacci.action file in the action directory

int32 order
int32[] sequence
int32[] partial_sequence

5 CMakeLists.txt build

find_package(rosidl_default_generators REQUIRED)


6 package.xml add dependencies





7 Build the package

colcon build --packages-select tutorial_interfaces

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