DataDescriptionObjectInterface Manual

Table of Contents

• About
• Interface
• Implementation
• Further Reading

About

maxon::DataDescriptionObjectInterface is an interface that can be used as a base for custom interfaces. It allows to add data descriptions to the reference object.

Interface

The maxon::DataDescriptionObjectInterface defines the maxon::DataDescriptionObjectInterface::GetObjectDescription() function. This function can be used to access the description from the given object. The needed argument can be constructed with maxon::CreateDataDictionaryReferenceObject().

  // This example creates a new object of a custom type. GetObjectDescription() is used to
  // get the data description of that instance. The attributes are printed to the console.
 
  // create new object
 
  const DescriptionElementRef element = DescriptionElementClass().Create() iferr_return;
  element.SetAttributeCount(2);
 
  // get description data
  maxon::DataDescription description;
 
  maxon::DataDictionary settings;
  maxon::DataDictionaryObjectRef dataRef = maxon::CreateDataDictionaryReferenceObject(&settings) iferr_return;
  const maxon::Id category = maxon::DATADESCRIPTION_CATEGORY_DATA;
  const maxon::LanguageRef language = maxon::Resource::GetDefaultLanguage();
  description = element.GetObjectDescription(category, language, dataRef) iferr_return;
 
  // list all attributes
 
  const auto attributes = description.GetEntries() iferr_return;
 
  for (const auto& attribute : attributes)
  {
    const maxon::InternedId ID = attribute.Get(maxon::DESCRIPTION::BASE::IDENTIFIER) iferr_return;
    const maxon::Id         dataType = attribute.Get(maxon::DESCRIPTION::DATA::BASE::DATATYPE) iferr_return;
    const maxon::Data       defaultData = attribute.Get(maxon::DESCRIPTION::DATA::BASE::DEFAULTVALUE) iferr_return;
 
    DiagnosticOutput("Attribute \"@\", of type @. Default value: @", ID, dataType, defaultData);
  }

Another function is maxon::DataDescriptionObjectInterface::GetObjectName(), which returns the name of the objects (maxon::OBJECT::BASE::NAME) for the given language.

Implementation

A custom interface can be based on maxon::DataDescriptionObjectInterface. The resulting reference object will store a data description. The default implementation of maxon::DataDescriptionObjectInterface is maxon::DataDescriptionObjectClass.

A custom implementation can re-implement maxon::DataDescriptionObjectInterface::GetObjectDescription() to modify the returned description.

// This example shows an implementation of an interface based on DataDescriptionObjectInterface.
// It implements GetObjectDescription() to edit the returned DataDescription.
 
// implementation of DescriptionElementInterface
class DescriptionElementImpl : public maxon::Component<DescriptionElementImpl, DescriptionElementInterface>
{
  // use the default implementation "DataDescriptionObjectClass"
  MAXON_COMPONENT(NORMAL, maxon::DataDescriptionObjectClass);
 
public:
  MAXON_METHOD void SetAttributeCount(maxon::Int count)
  {
    _count = count;
  }
 
  MAXON_METHOD maxon::Result<maxon::DataDescription> GetObjectDescription(const maxon::Id& category, const maxon::LanguageRef& language, const maxon::DataDictionaryObjectRef& objectData) const
  {
    iferr_scope;
 
    // load default description
    maxon::DataDescription description = super.GetObjectDescription(category, language, objectData) iferr_return;
 
    // check category
    if (category == maxon::DATADESCRIPTION_CATEGORY_DATA)
    {
      // add dynamic attributes of the type "maxon::String"
      for (maxon::Int i = 0; i < _count; ++i)
      {
        // generate dynamic ID
        const maxon::String number = maxon::String::IntToString(i);
        const maxon::String identifier("net.maxonexample.class.descriptionElement.dynamic_"_s + number);
        maxon::InternedId   dynamicID;
        dynamicID.Init(identifier) iferr_return;
 
        const maxon::Id stringDataType = maxon::GetDataType<maxon::String>()->GetId();
 
        // set attribute settings
        maxon::DataDictionary dynamicAttribute;
        dynamicAttribute.Set(maxon::DESCRIPTION::BASE::IDENTIFIER, dynamicID) iferr_return;
        dynamicAttribute.Set(maxon::DESCRIPTION::DATA::BASE::DATATYPE, stringDataType) iferr_return;
        dynamicAttribute.Set(maxon::DESCRIPTION::DATA::BASE::DEFAULTVALUE, "Hello World"_s) iferr_return;
 
        // add new attribute
        description.SetEntry(dynamicAttribute) iferr_return;
      }
    }
 
    return description;
  }
 
private:
  maxon::Int _count = 0;  
};

Further Reading

• Data Descriptions
• Data Description Categories and Keys
• DataDescription Manual
• DataDictionary Manual
• Resource IDs