Use this ROS2 package to create custom interfaces, eg. topic (*.msg) and/or service (*.srv) files.  
This package must only be used for interface files and __no__ Python scripts.  

The following steps describe how to create a new custom topic or service.   

## 1. Create new interface file
Topic *.msg files got into `msg` directory,  
Service *.srv files got into `srv` directory.  

Create these files according to the example on this [instructions page](https://docs.ros.org/en/foxy/Tutorials/Writing-A-Simple-Py-Service-And-Client.html).

## 2. CMakeLists.txt
Edit the `CMakeLists.txt` file by adding the newly created *.msg or *.srv files to this part:
```cmake
rosidl_generate_interfaces(${PROJECT_NAME}
  "msg/CustomMsg1.msg"
  "msg/CustomMsg2.msg"
  "srv/CustomSrv1.srv"
  DEPENDENCIES builtin_interfaces
 )
```

## 3. Build colcon workspace
Move back to the root of your _colcon_ workspace and rebuild it: `colcon build --symlink-install`  
It should build without any errors. If you encounter errors fix these before continuing.

After a successful build you must __close and reopen all terminals__ in order to source the newly built workspace. For this to happen you must have edited _.bashrc_ and added your current workspace (`sudo nano ~/.bashrc` and follow [this example](https://egit.irs.uni-stuttgart.de/RoverLehre/ROS2_pubsub/src/branch/master/non-ros-files/bashrc_overlay.bash)).

## 4. Import interfaces
Import the newly created interfaces into the Python scripts. These scripts must be located in _Python packages_ inside the same workspace (or another _sourced_ workspace):  
* Topics:  
```python
from custom_interfaces.msg import CustomMsg1
```

* Services:  
```python
from custom_interfaces.srv import CustomSrv1
```
Now you can work with your custom interface in order to exchange custom information between nodes.