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Some Automation controllers do not support the use of SAFEARRAYs. For this reason, arrays and sequences can also be mapped
to OLE collection objects.
A collection object allows generic iteration over its elements. While there is no explicit ICollection type interface, OLE
does specify guidelines on the properties and methods a collection interface should export.
// ODL[odl, dual, uuid(...)]interface DICollection: IDispatch {
[propget] HRESULT Count([retval,out] long * count);[propget, id(DISPID_VALUE)] HRESULT Item([in] long index, [retval,out] VARIANT * val);
[propput, id(DISPID_VALUE)] HRESULT Item([in] long index,[in] VARIANT val);[propget, id(NEW_ENUM)] HRESULT _NewEnum([retval, out] IEnumVARIANT * newEnum);
}
The UUID for DICollection is:
{A8B553C9-3B72-11cf-BBFC-444553540000}
This interface can also be implemented as generic (nondual) Automation Interface, in which case it is named DCollection and
its UUID is:
{E977F909-3B75-11cf-BBFC-444553540000}
In controller scripting languages such as VBA in MS-Excel, the FOR...EACH language construct can automatically iterate over
a collection object such as that previously described.
‘ Visual Basic:Dim doc as ObjectFor Each doc in DocumentCollectiondoc.Visible = FalseNext doc
The specification of DISPID_VALUE as the id() for the Item property means that access code like the following is possible.
‘ Visual Basic:Dim docs as ObjectSet docs = SomeCollection
docs(4).Visible = False
Multidimensional arrays can be mapped to collections of collections with access code similar to the following.
‘ Visual BasicSet docs = SomeCollection
docs.Item(4).Item(5).Visible = False
If the Collection mapping for OMG IDL Arrays and Sequences is chosen, then the signatures for operations accepting SAFEARRAYs
should be modified to accept a VARIANT instead. In addition, the implementation code for the View wrapper method should detect
the kind of object being passed.