DG Kernel (ActiveX) Documentation


Skip Navigation Links.
Start page
Quick Start
Search Page
Installation
What is new
Upgrading Native Apps
Licensing
Expand ModelsModels
Collapse DG Kernel ControlsDG Kernel Controls
Expand API ReferenceAPI Reference
Expand ViewsViews
Expand Samples and TutorialsSamples and Tutorials
Expand GraphicsGraphics
Expand Math ObjectsMath Objects
Expand DeprecatedDeprecated
Redistribution
Model Viewer
Open Source
Support
Skip Navigation LinksHome Page > DG Kernel Controls > Programmatic Functionality > Queries Go to DGKC docs Search Documentation


Interface Queries

Operation of obtaining and interface from an object with QueryInterface() in C++ or coercion/cast in other languages or with a call to some method like GetModel() is called Simple Query . Normally to get access to a specific functionality it is needed to traverse several levels in the hierarchy of interfaces. Such a sequence of simple queries is called extended query (or just query). Its description in textual form is called query path. 

Sample of a query path: DG Kernel > GetModel() > IModel_DG > GetEntityAt() > IEntity_DG

In some (rare) situations, the result of a query can depend on the query path. For example for an entity with 3DS geometry, path IEntity_DG > IArray returns IArray of its child entities, but path IEntity_DG > IAxiBase > IArray returns IArray of its base knots. Such queries are called Context-Dependent Query

Description of specific interfaces describes situations when the interface can be involved in a context-dependent query. Context-dependent queries should be carried out without any other queries from the involved interfaces. Specific cases may have alleviations of this rule.