Datalayer hierarchy in c++

[osamaayoub]

Hello,

I am trying to create a hierarchy of nodes and folder in the datalayer and I am facing an issue with that.

When I create a folder on the datalayer which contains only nodes of different types, it goes smoothely without any problem. The problem starts when I want to create a Folder that contains nodes and other folders which also contains nodes.

The goal hierarchy:

• Root
  • node1 (boolean node)
  • parent1
    • child1 (boolean node)

I tried several ways of doing that as follows: (The arguments of RegisterNodes are the name of the node, type and array length, I customized it to achieve certain goals)

Trial1:

auto Object = new ProviderNodeAllData(dlProvider, "Root", true);
Object->RegisterNodes("node1", "bool8", 0);
Object = new ProviderNodeAllData(dlProvider, "Root", true);
Object->RegisterNodes("Parent1/Child1", "bool8", 0);

Trial2:

 auto Object = new ProviderNodeAllData(dlProvider, "Root", true);
 Object->RegisterNodes("node1", "bool8", 0);
 Object = new ProviderNodeAllData(dlProvider, "Root/Parent1", true);
 Object->RegisterNodes("child1", "bool8", 0);

Trial3:

auto Object = new ProviderNodeAllData(dlProvider, "Root", true);
Object->RegisterNodes("node1", "bool8", 0);
auto Object2 = new ProviderNodeAllData(dlProvider, "Root/Parent1", true);
Object2->RegisterNodes("child1", "bool8", 0);

 Trial4:

auto Object = new ProviderNodeAllData(dlProvider, "Root", true);
Object->RegisterNodes("node1", "bool8", 0);
auto Object2 = new ProviderNodeAllData(dlProvider, "Root", true);
Object2->RegisterNodes("Parent1/child1", "bool8", 0);

 The issue is as shown in the picture, the folder doesn't have metadata:

Here is a part of registerNodes function:

void ProviderNodeAllData::RegisterNodes(std::string name, std::string type, int32_t ArrayLength)
{

  comm::datalayer::DlResult result;
  comm::datalayer::Variant data;

  result = _provider->registerNode(_addressBase + "**", this);
  //These if statments checks the datatype of the node to be registered and create that node for non arrays
  if(type == "bool8" && ArrayLength == 0){
    result = data.setValue(false);
    createDataContainer(result, name, data);
.
.
.
.
}

Your help is highly appreciated.

Regards,

Osama

[nickH · Accepted solution]

Hello Osama, 

the problem in the Data Layer are the missing metadata for your folder. Metadata for nodes can be provided as follows (see documentation) :

• Via the ‪onMetadata()‬ of a ‪ProviderNodes‬

• Or via a metadata database (MDDB)

In the sample samples-cpp/datalayer.register.node you can see an example where this is done via the metadata database. A metadata database is provided via CSV file. I changed the sample and tested it for a similar structure like you have (see screenshot). 

You can try out my main.cpp and metadata.csv if you paste it into the sdk-sample (sample-cpp/datalayer.register.node).

Best regards, 

Nick

[osamaayoub]

Thank you for your reply it is indeed helpful, I would prefer to use the first method without involving .csv files. Shouldn't the function:

comm::datalayer::Variant ProviderNodeAllData::createMetadata(const comm::datalayer::Variant &data, const std::string &address)

Shouldn't it take care of creating the metadata by itself? I can see that it is called when a new ProviderNodeAllData object is created.

I can also see inside createMetadata that it detect that the node parent1 is a folder class which is "7" and when it runs everything goes just fine. If I should use onMetadata() manually, is there something similar in the samples that I missed? 

[osamaayoub · Accepted solution]

Hello again,

I discovered the main reason behind the problem which is: The _addressBase is not being added correctly when I go deeper in the structure because of this line in RegisterNodes function

result = _provider->registerNode(_addressBase + "**", this);

So I changed it to:

result = _provider->registerNode(_addressBase , this);

To update the address base and get the metaData correctly when I have a deep structure.

Thank you so much for your help, it lead me to look deeper into onMetaData() which solved the problem for me.

Cheers,

Osama

[nickH]

Great to read that you discovered the problem. And many thanks for sharing the solution!

Regards, 

Nick

[osamaayoub]

One last thing, the line of code that I changed is actually from the samples-cpp allDataProvider, I don't know if it is left like this intentionally or not, but I would suggest to add a comment there so no one would have such an issue later 🙂