COMARRAY( ) Function

  • Article

Specifies how arrays are passed to COM objects.

COMARRAY(oObject [, nNewValue])

Return Values

Numeric

Parameters

  • oObject
    An object reference to the COM object.

  • nNewValue
    Specifies how an array is passed to the COM object specified with oObject. The following table lists the settings for nNewValue and how the array is passed to the COM object.

    nNewValue Description
    0 The array is a zero based array, and it is passed by value.
    1 (Default) The array is a one based array, and it is passed by value. Compatible with earlier versions of Visual FoxPro.
    10 The array is a zero based array, and it is passed by reference.
    11 The array is a one based array, and it is passed by reference.
    100 The array is a fixed size array and cannot be redimensioned.

    Issue COMARRAY( ) without the nNewValue argument to return the current setting.

Remarks

Earlier versions of Visual FoxPro can only pass arrays to COM objects by value. Also, the array passed to the COM object is assumed be a one based array, meaning that the first element, row, and column in the array is referenced with 1.

However, some COM objects require that arrays passed to them be passed by reference, or the array passed is zero based (the first element, row, and column in the array is referenced with 0), or both. COMARRAY( ) lets you specify how the array is passed to the COM object, and assumes you know how the array should be passed to the COM object.

Note that COMARRAY( ) is only used when arrays are passed to COM objects using the following syntax:

oComObject.Method(@MyArray)

If the @ token is omitted, only the first element of the array is passed to the COM object and COMARRAY( ) has no effect.

The additive nValue of 100 as used in the following example enables you to prevent redimensioning of an array (to run this example, first build the class definition into a DLL named "t1.dll"). You should check for possible errors after calling the server, in case the server attempts to redimension the array.

LOCAL loSvr, laTest
loSvr = NEWOBJECT("t1.arrayhandler")
DIMENSION laTest[10]
laTest=3
? COMARRAY(loSvr,11 + 100)
* The COM server will return an error on the next line of code
* because arrays passed to loSvr will not allow re-dimensioning.
loSvr.RedimensionArray(@laTest,4)
? ALEN(laTest)

DEFINE CLASS ARRAYHANDLER AS CUSTOM OLEPUBLIC
    PROCEDURE RedimensionArray(aArray, nRows)
        DIME aArray[nRows]
    ENDPROC
ENDDEFINE

See Also

COMCLASSINFO( ) | CREATEOBJECT( ) | GETOBJECT( )