The DCOM Wrapper maps a structure definition to an object inside an automation object. The structure can be created and modified independently of program calls, e.g., a structure object can be created once and can be used in one or more programs several times - it is always the same object with the same information. It is also possible to retrieve a structure via a program call and use it in another program.
This document covers the following topics:
A structure definition has always a name like a program name. The
difference is that a structure will be defined with the keyword STRUCT.
Furthermore a structure cannot be called like a program. A structure represents
only a data object to be used with the programs. A structure has more the
character of a group but unlike a group a structure will not be created
automatically by the DCOM Wrapper object. The user has to create a
structure with the corresponding functions.
If a structure has embedded structures, first create the parent structure and then the embedded structures.
If a structure has embedded groups, the embedded groups are created automatically when the parent structure. is created.
If a group has embedded structures, the embedded structures must be created by the user. The parent group self is created by DCOM Wrapper object.
LIBRARY 'STRUCTLIB' is
STRUCT 'User' Is
DEFINE DATA PARAMETER
1 UserId (AV)
1 Password (AV)
END-DEFINE
PROGRAM 'Prog01' Is
DEFINE DATA PARAMETER
1 ID ('User')
1 something (AV)
END-DEFINE
PROGRAM 'Prog02' Is
DEFINE DATA PARAMETER
1 ID ('User')
1 somewhere (AV)
END-DEFINE
'first create an instance of the DCOM Wrapper Object Dim obj As New STRUCTLIB 'Declares a variable for our User structure Dim userobj As Object 'Declares a variable for the second parameter Dim something as String 'create the 'User' structure Set userobj = obj.createStructure_User 'now you can access the structure items userobj.UserId = "userid" userobj.Password = "password" something = "Hello" 'call the DCOM object obj.Prog01 userobj, something 'the same userobj could now used by obj.Prog02. Please consider that 'obj.Prog01 may have changed the data if you reuse userobj. 'get the response from the server and show the message a message box MsgBox "User ID = " & userobj.UserId
Structures can also be defined in a more complex manner. This example shows a definition of a structure in a structure. In this example the customer can have multiple addresses and could have bought multiple products. The following example may not make sense, it is only an example to show the handling of complex structures and embedded structures.
LIBRARY 'CUSTLIB' is
STRUCT 'AddressStruct' Is
DEFINE DATA PARAMETER
1 Street (A255)
1 City (A255)
1 Postal_Code (A32)
END-DEFINE
STRUCT 'CustomerStruct' Is
DEFINE DATA PARAMETER
1 Name (A255)
1 Address ('AddressStruct'/V)
END-DEFINE
STRUCT 'SalesStruct' Is
DEFINE DATA PARAMETER
1 ProductName (A255)
1 ProductID (PU20)
1 SalesDate (D)
1 SalesVolume (N12.2)
END-DEFINE
PROGRAM 'CustomerInformation' is
DEFINE DATA PARAMETER
1 Customer ('CustomerStruct')
1 SalesData ('SalesStruct'/V)
END-DEFINE
'first create an instance of the DCOM Wrapper Object Dim obj As New CUSTLIB 'Declares an array of variables for our sales structure Dim salesobj() As Object 'Declares a variable for our customer structure Dim custobj As Object 'Declares a variable for our address structure Dim Addressobj As Object 'temp strings Dim addressdata As String Dim salesdata As String Dim i As Integer 'create the 'Customer' structure Set custobj = obj.createStructure_CustomerStruct 'redim the Customer structure to the size 2 in the first dimension. custobj.redim_address 2, 1, 0, 0, 0 'set the name of the customer custobj.Name = "Customer A" 'create a new address structure Set Addressobj = obj.createStructure_AddressStruct 'fill the data items of this structure Addressobj.street = "back street" Addressobj.city = "back town" Addressobj.postal_code = "12345" 'assign the address structure to the first array item of the 'Customer structure. custobj.address_indexAccess(0) = Addressobj 'create the second 'Customer' structure Set Addressobj = obj.createStructure_AddressStruct 'fill the data items of this structure, too Addressobj.street = "front street" Addressobj.city = "front town" Addressobj.postal_code = "54321" 'assign the address structure to the second array item of the 'Customer structure. custobj.address_indexAccess(1) = Addressobj 'Redim the sales array object, the salesobj has now one 'array item ReDim salesobj(0) 'create a new sales structure Set salesobj(0) = obj.createStructure_SalesStruct 'fill the data items of this structure salesobj(0).ProductName = "phone" salesobj(0).productid = "12547" salesobj(0).salesdate = Now salesobj(0).salesvolume = "99.91" 'call the DCOM object with the two parameters. obj.CustomerInformation custobj, salesobj 'now show the received data addressdata = "" addressdata = custobj.Name & vbCrLf 'please note that you need to use the DCOM Wrapper special function 'to access the embedded structures. For i = 0 To custobj.get_address_UpperBound(1, 0) 'get a pointer to the address data Set Addressobj = custobj.address_indexAccess(i) 'pick the data from the address structure addressdata = addressdata & Addressobj.street & ";" & _ Addressobj.city & vbCrLf Next 'please note that you don't have a special function to access 'a structure array for the data on the first level. salesdata = addressdata & vbCrLf ' show the other sales For i = 0 To UBound(salesobj) 'pick the data from the address structure salesdata = salesdata & salesobj(i).ProductName & ";" & _ CLng(salesobj(i).salesvolume) & vbCrLf Next 'now show data in a message box MsgBox (salesdata)
The DCOM Wrapper creates a function for each structure
definition. The function is always a member of the library object and has
always the same naming template. It begins with the keyword
createStructure_ with a following structure name. This function
returns an IDispatch object pointer to a new valid structure data object.
STDMETHODIMP createStructure_<structure name>( IDispatch ** );
The method createStructure_<structure
name> creates a new instance of the named original structure, a
pointer to this structure is returned.
LIBRARY 'EXAMPLELIB' is STRUCT 'SData' Is DEFINE DATA PARAMETER 1 Name (A255) 1 Address (A255) END-DEFINE . . . .
Dim sdata As Object Dim obj As New EXAMPLELIB set sdata = obj.createStructure_SData
IStructure_SData sdata; EXAMPLELIBClass obj = new EXAMPLELIBClass(); sdata = (IStructure_SData)obj.createStructure_SData();