Register multiple flatbuffer types in Data Layer

[AlexStepanov]

I want to use multiple different flatbuffers in my application, but I can't register more than one flatbuffer as a type in the data layer.

I extended the datalayer.register.node example to include a second flatbuffer (called sampleScheme2.fbs). Now when I start the application, I always see that registerType fails with the message "DL_INVALID_VALUE" for the second flatbuffer. 
If I call registerType for sampleScheme2.fbs first, than sampleScheme.fbs returns "DL_INVALID_VALUE" when calling registerType.

Registering the nodes works without any problems.

Do I have to create a new data layer provider for each flatbuffer?

[CodeShepherd · Accepted solution]

Sorry for the late reply.

Of course it is possible to register several flatbuffers in one app. I adapted the registernode example of the SDK for ctrlx AUTOMATION in version 1.10:

1. Added new schema file "mysampleSchema.fbs:
   

   // IDL file for sample schema.
   namespace mysample.myschema;
   table InertialValue {    x:short;    y:short;    z:short;    a:short;}
   root_type InertialValue;​

2. Extended CMakeLists.txt:
   

   ...
   
   # Flatbuffers
   set (FLATBUFFERS_FLATC_EXECUTABLE ${USER_DEPENDENCY_DIR}/bin/oss.flatbuffers/linux-gcc-x64/release/flatc)
   set (FLATBUFFERS_INCLUDE_DIR ${USER_DEPENDENCY_DIR}/include/oss.flatbuffers/oss.flatbuffers)
   include (${USER_DEPENDENCY_DIR}/cmake/oss.flatbuffers/FindFlatBuffers.cmake)
   set( FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS "--gen-object-api")
   build_flatbuffers("sampleSchema.fbs" "" "registernodeflatbuffers" "${CMAKE_CURRENT_LIST_DIR}" "${CMAKE_CURRENT_LIST_DIR}" "${CMAKE_CURRENT_LIST_DIR}/bfbs" "")
   build_flatbuffers("mysampleSchema.fbs" "" "myregisternodeflatbuffers" "${CMAKE_CURRENT_LIST_DIR}" "${CMAKE_CURRENT_LIST_DIR}" "${CMAKE_CURRENT_LIST_DIR}/bfbs" "")
   
   ...​
   
   # Define Executables to add from project files and their depending source files
   add_executable( ${TARGET_PROJECT_NAME}	${SOURCE_FILES_REGISTERNODE}  )
   add_dependencies(${TARGET_PROJECT_NAME} registernodeflatbuffers)
   add_dependencies(${TARGET_PROJECT_NAME} myregisternodeflatbuffers)

3. Adapted main.cpp:
   

   ...
   
   #include "sampleSchema_generated.h"
   #include "mysampleSchema_generated.h"
   
   ...
   
   // Read function of metadata of an object. Function will be called whenever a node should be written.
     virtual void onMetadata(const std::string &address, const comm::datalayer::IProviderNode::ResponseCallback &callback) override  {
       flatbuffers::FlatBufferBuilder builder;
       flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<comm::datalayer::Reference>>> references;
       flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<comm::datalayer::Reference>>> references2;
       auto emptyString = builder.CreateString("This is a Description");
   
       if (address.compare("myData/myFlatbuffer") == 0)    {
         flatbuffers::Offset<comm::datalayer::Reference> vecReferences[] =      {
           comm::datalayer::CreateReferenceDirect(builder, "readType", "types/sampleSchema/inertialValue"),      };
   
         references = builder.CreateVectorOfSortedTables(vecReferences, 1);    }
       else if (address.compare("myData/myFlatbuffer2") == 0)    {
         flatbuffers::Offset<comm::datalayer::Reference> vecReferences[] =      {
           comm::datalayer::CreateReferenceDirect(builder, "readType", "types/mysampleSchema/inertialValue"),      };
   
         references2 = builder.CreateVectorOfSortedTables(vecReferences, 1);      }
   
       // Set allowed operations
       comm::datalayer::AllowedOperationsBuilder allowedOperations(builder);
       allowedOperations.add_read(true);
       allowedOperations.add_write(false);
       allowedOperations.add_create(true);
       allowedOperations.add_delete_(false);
       auto operations = allowedOperations.Finish();
   
       // Create metadata
       comm::datalayer::MetadataBuilder metadata(builder);
       metadata.add_description(emptyString);
       metadata.add_descriptionUrl(emptyString);
       metadata.add_operations(operations);
       if (address.compare("myData/myFlatbuffer") == 0)    {
         metadata.add_references(references);    }
       else if (address.compare("myData/myFlatbuffer2") == 0)       {
         metadata.add_references(references2);    } 
       auto metaFinished = metadata.Finish();
       builder.Finish(metaFinished);
   ​
   ... 
   
   // Create dummy flatbuffer data
     flatbuffers::FlatBufferBuilder builder2;
     auto actInertialValue2 = mysample::myschema::CreateInertialValue(builder2, 33, -427, 911, 42);    
     builder2.Finish(actInertialValue2);
     comm::datalayer::Variant myFlatbuffer2;
     myFlatbuffer2.shareFlatbuffers(builder2);
   
     // Register type of flatbuffer value
     // If running on SNAP environment, use $SNAP environment variable for register the bfbs
     std::string bfbsPath2 = getenv("SNAP") != nullptr ? getenv("SNAP") : "bfbs";
     bfbsPath2 += "/sampleSchema.bfbs";
     std::cout << bfbsPath2 << std::endl;
     result = myProvider->registerType("types/mysampleSchema/inertialValue", bfbsPath2);
     if(STATUS_FAILED(result))  {
       std::cout << "Register type 'types/mysampleSchema/inertialValue' failed with: " << result.toString() << std::endl;  }
     else  {
       std::cout << "Register type 'types/mysampleSchema/inertialValue' was successful!" << std::endl;  }
   
       // Register a node as flatbuffer value
     result = myProvider->registerNode("myData/myFlatbuffer2", new MyProviderNode(myFlatbuffer2));
     if(STATUS_FAILED(result))  {
       std::cout << "Register node 'myData/myFlatbuffer2' failed with: " << result.toString() << std::endl;  }
     else  {
       std::cout << "Register node 'myData/myFlatbuffer2' was successful!" << std::endl;  }
   
   ...
   
     // Unregister type and nodes
     myProvider->unregisterType("types/sampleSchema/inertialValue");
     myProvider->unregisterType("types/mysampleSchema/inertialValue");  
   
   ...

4. Run application:
   

    

[David08]

Hello,

I am interested in making a very similar application to be able to send data to the PLC by Rest API in a single JSON file.
I've started to test the ResgisterNode example but VSCode is giving me an error because it can't find the "SampleSchema_generated.h" library.
How can I fix it, I have no experience with VSCode.

I'm using SDK 1.10 in a virtual machine with Ubuntu 18

Thanks in advance.

[CodeShepherd]

The "xxx_generated.h" file will be generated by Cmake (code: step number 2 in previous post) just by following the build procedure.

1. Open example in VSC
2. Choose Cmake build option and wait for configuration to be finished:
   
3. Build your project and the file will appear:
   
   

[AlexStepanov]

I still had problems, but I finally found the error!

strcat shouldn't be used with getenv, because the first arguments gets modified. See std::strcat - cppreference.com

Modifying the lines to something like this resolves the issues when running the app in a snap package:

std::string bfbsPath = getenv("SNAP") != nullptr ? getenv("SNAP") : "bfbs";
bfbsPath += "/sampleSchema.bfbs")

...

std::string bfbsPath2 = getenv("SNAP") != nullptr ? getenv("SNAP") : "bfbs";
bfbsPath2 += "/sampleSchema.bfbs";

[CodeShepherd]

Thanks for mentioning we will check that and improve our example.