COMTypedList-class: Classes for representing DCOM objects that have list-like...

In omegahat/RDCOMClient: R-DCOM client

Classes for representing DCOM objects that have list-like facilities

Description

These classes extend the basic COMList. They are used to represent DCOM types that have methods that support a list-like interface. In Office applications, this means that they have methods named Item and Count which correspond to index accessors ([[) and length in R. We can therefore make these objects feel more like R lists using methods defined for these classes.

Like COMList-class, these classes are not intended to be used directly, but are to be used in creating derived or sub-classes.

These particular classes provide additional functionality for the COMList-class by specifying the type of the elements. COMTypedList knows that its elements have a type/class name given by the singular of its own class. For example, if we had a class named Workbooks that extended COMTypedList, then elements returned via its Item method would be coerced to class Workbook the singular of Workbooks.

The class COMTypedNamedList does essentially the same thing, but does not rely on the class name of its elements being the singular form of its own class name. Instead, the class name is stored with the COMTypedNamedList object and is used to coerce an element returned from the Item method to the appropriate R class. (If we had class slots in the S4 system, we would use that rather than putting the name into each instance of a class. However, the overhead is small.) This is used, for example, in the case of our Workbooks illustration above. In Excel, the Workbooks type behaves like a list but returns elements which are of class _Workbook. In this case, the name field in the derived class Workbooks would be _Workbook and elements would be coerced to that R type.

These classes form part of the run-time infrastructure for "compiled" or pre-processed classes to DCOM interfaces that are generated from the type library describing a collection of COM interfaces. See the SWinTypeLibs package and the generateInterface function.

Objects from the Class

Objects can be created from these classes manually using the familiar new function. However, when used in the "compiled" DCOM interfaces, they are automatically created as return values or arguments in methods where appropriate.

Slots

ref:

Object of class "externalptr", inherited

name:

character string (i.e. vector of length 1). This is the field in the COMTypedNamedList that specifies the name of the class for an element of the list.

Extends

Class "COMList", directly. Class "COMIDispatch", by class "COMList". Class "IUnknown", by class "COMList".

Methods

[[

signature(x = "COMTypedList", i = "ANY"): get the i-th element of the DCOM list and coerce the result to the appropriate type specified by the type of elements associated with the class.

Author(s)

Duncan Temple Lang ([e-mail])

References

http://www.omegahat.net/RDCOMClient http://www.omegahat.net/RDCOMServer http://www.omegahat.net/SWinTypeLibs http://www.omegahat.net/SWinRegistry

See Also

COMList-class .COM

omegahat/RDCOMClient documentation built on July 24, 2022, 5:45 a.m.