Native Objects

The objects produced by native modules are not restricted to m types. For instance, the streams returned by io.open are native objects which cannot be manipulated from within m, only by module io and a few other modules.

But native objects are not restricted to streams: an instance of any subclass of CBase can be wrapped into a native object. When doing so, the instance will automatically be deleted if the native object containing it is freed by garbage collection.

Each native object has a type which is a zero terminated character string. The type is used to check for a particular object type (C++ runtime types are not supported by Symbian), and when converting the object to a string, e.g. when printing it to the console. For instance, native streams have the type

/** The type of all native I/O streams. */ static const char * const TYPE = "stream";

Native objects are created by the following function from class Runtime:

Runtime::Value NewNativeL(CBase *obj, const char *type);
Creates a new native object. The object obj must not be on the cleanup stack, and is destroyed when this function leaves.

To access native objects, Runtime::Value offers the following methods:

TBool IsNative() const;
Checks whether this value is a native object.
NativeObject &GetNativeL() const;
Gets this value as a native object, leaving if it isn't a native object.
CBase *GetNativeObjL(const char *type) const;
Gets the object defined by this native object. Leaves if this isn't a native object, or if it has a different type.

And here is a sample fragment using native objects:

class MyObject : public CBase { public: static const char * const TYPE = "myobject"; static MyObject *NewL(); ... TInt count() const; } Runtime::Value ExecuteL(TInt index, Runtime::Value *params, TInt paramCount, TRequestStatus &status) { MyObject *obj; Runtime::Value result; switch (index) { case NewFunction: // create a native object around a MyObject instance obj = MyObject::NewL(); &nbs