WMP createQuery (Pointer Question)

[William Fauver]

I'm struggling with pointers for WMP createQuery. Any expert advice is welcome.

'================================================================================
LOCAL vQuery AS VARIANT 'IN pQuery AS WMPlayerIWMPQuery
'================================================================================
LOCAL vAttribute AS VARIANT 'IN bstrAttribute AS STRING
LOCAL vOperator AS VARIANT 'IN bstrOperator AS STRING
LOCAL vValue AS VARIANT 'IN bstrValue AS STRING
'================================================================================
LOCAL pQuery AS VARIANT PTR 'IN pQuery AS WMPlayerIWMPQuery
LOCAL vMediaType AS VARIANT 'IN bstrMediaType AS STRING
LOCAL vSortAttribute AS VARIANT 'IN bstrSortAttribute AS STRING
LOCAL vBool AS VARIANT 'IN fSortAscending AS LONG
'================================================================================
LOCAL vPlaylist AS VARIANT
'================================================================================

OBJECT CALL oWMPlayer.mediaCollection.createQuery() TO vQuery

vAttribute = "Title"
vOperator = "Contains"
vValue = "Blues"

OBJECT CALL oWMPlayer.mediaCollection.createQuery().addCondition(vAttribute, vOperator, vValue)

vQuery = ??? (POINTER to Query object)
vMediaType = "Title"
vSortAttribute = ""
vBool = %FALSE

OBJECT CALL oWMPlayer.mediaCollection.getPlaylistByQuery(vQuery, vMediaType, vSortAttribute, vBool) TO vPlaylist

OBJECT LET oWMPlayer.currentPlaylist = vPlayList

[Michael Mattias]

>vSortAttribute = ""

I just had similar thing with ADO... instead of null string here, try LET vSortAttribute = EMPTY

Pointer to query (vQuery) could be VARPTR (vQuery), or it could be the OBJPTR of whatever object the CreateQuery method creates...

eg

LOCAL oQUeryObject AS (query object interface) 
OBJECT CALL  ....CreateQuery  to VQuery 
LET   oQueryObject = vQuery
pQueryObject = OBJPTR (oQueryObject)

But I would think just leaving it in the variant returned by CreateQuery would be fine... that is, once you get vQuery, leave it alone.

Let me guess, no useful error codes?

[Michael Mattias]

This should be the doc you want..

http://msdn.microsoft.com/en-us/library/ms867697.aspx

[José Roca]

One of the problems is that using the compound syntax he is creating two queries: an empty one with OBJECT CALL oWMPlayer.mediaCollection.createQuery() TO vQuery, and a second one with OBJECT CALL oWMPlayer.mediaCollection.createQuery().addCondition(vAttribute, vOperator, vValue), which has a condition added but for what he has not a reference.

Try the following:

OBJECT CALL oWMPlayer.mediaCollection.createQuery() TO vQuery
DIM oQuery AS DISPATCH ' (or AS IWMPQuery if you are using early binding)
oQuery = vQuery

vAttribute = "Title"
vOperator = "Contains"
vValue = "Blues"

OBJECT CALL oQuery.addCondition(vAttribute, vOperator, vValue)

vMediaType = "Title"
vSortAttribute = ""
vBool = %FALSE

OBJECT CALL oWMPlayer.mediaCollection.getPlaylistByQuery(vQuery, vMediaType, vSortAttribute, vBool) TO vPlaylist

OBJECT LET oWMPlayer.currentPlaylist = vPlayList

Another potential problem can be the boolean parameter (vBool). Some servers just check for true or false, but others are very picky and also check if it is a VT_BOOL variant.

If this is the case, you can use this function to convert vBool in a VT_BOOL variant:

' ========================================================================================
' Initializes a VARIANT structure with a Boolean value.
' ========================================================================================
FUNCTION PB_InitVariantFromBoolean (BYVAL boolVal AS INTEGER, BYREF pvar AS VARIANT) AS LONG
   LOCAL pv AS VARIANTAPI PTR
   IF VARPTR(pvar) = 0 THEN
      FUNCTION = %E_INVALIDARG
      EXIT FUNCTION
   END IF
   pvar = EMPTY                               ' Make sure is empty to avoid memory leaks
   pv = VARPTR(pvar)                          ' Get the VARIANT address
   @pv.vt = %VT_BOOL                          ' Mark it as containing a boolean value
   @pv.boolVal = IIF&(boolVal <> 0, -1, 0)    ' Set the value
   FUNCTION = %S_OK
END FUNCTION
' ========================================================================================

[William Fauver]

WMP createQuery (Pointer Question)

Thank you very much! Creating the oQuery DISPATCH was the solution. The server accepts %FALSE, so I didn't need to initialize the variant as you suggested. I also changed vMediaType to "audio" (my error).

LOCAL vQuery AS VARIANT
OBJECT CALL oWMPlayer.mediaCollection.createQuery() TO vQuery
LOCAL vAttribute AS VARIANT
LOCAL vOperator AS VARIANT
LOCAL vValue AS VARIANT
vAttribute = "Author"
vOperator = "Contains"
vValue = "Beethoven"
LOCAL oQuery AS DISPATCH
oQuery = vQuery
OBJECT CALL oQuery.addCondition(vAttribute, vOperator, vValue)
LOCAL vMediaType AS VARIANT
LOCAL vSortAttribute AS VARIANT
LOCAL vBool AS VARIANT
vMediaType = "audio"
vSortAttribute = EMPTY
vBool = %FALSE
LOCAL vPlaylist AS VARIANT
OBJECT CALL oWMPlayer.mediaCollection.getPlaylistByQuery(vQuery, vMediaType, vSortAttribute, vBool) TO vPlaylist
OBJECT LET oWMPlayer.currentPlaylist = vPlayList