Run-time type information

The Core Library provides its own run-time type information (RTTI) mechanism that can be used in place of the one that C++ offers. This can be useful in cases where RTTI isn’t properly supported by particular toolchain or when RTTI is disabled due to other constraints. The RTTI implementation in Core allows to perform safe typecasts using the Core::Portable::core_cast template function and supporting macros.

Using RTTI

To use RTTI with your own objects, your class needs to derive from Core::Portable::ITypeInfo and implement the Core::Portable::ITypeInfo::castTo function. This is usually done by using the DECLARE_CORE_CLASS macro in the class declaration. The following example demonstrates how to add type information to a class.

#include "core/portable/coretypeinfo.h"

class Parameter: public TypedObject
{
public:
  DECLARE_CORE_CLASS ('Para', Parameter, TypedObject)

  Parameter (const ParamInfo& info, bool ownsInfo = false);
  ~Parameter ();

  // ... other declarations following
};

In this example the Core::Portable::Parameter class derives from Core::Portable::TypeInfo. The TypeInfo class again derives directly from ITypeInfo and provides a simple implementation of castTo that always returns nullptr. The DECLARE_CORE_CLASS macro then assigns the type identifier 'Para' to the class and also overrides the castTo function which returns a pointer to the object itself when the type identifier matches or passes the call up to the derived class. Other classes deriving from Core::Portable::Parameter (like Core::Portable::NumericParam or Core::Portable::ListParam) do the same to implement RTTI.

In order to perform a dynamic typecast on an object, use the Core::Portable::core_cast function as shown as in the following code snippet.

Parameter* param = ...

NumericParam* numParam = core_cast<NumericParam> (param);
if(numParam != nullptr)
{
  // This is a NumericParam object and its safe to call it's functions.
}
else
{
  // Not a NumericParam
}

If you must obtain the type identifier for a particular class use the Core::Portable::core_typeid template function.

ITypedObject::TypeId id = core_typeid<NumericParam> ();
// id equals 'NPar'