Byte to variant requires AS?

[Mike Doty]

Does assigning a byte to a variant require using AS or is this an error in my code?

#DIM ALL
FUNCTION PBMAIN AS LONG
 LOCAL b AS BYTE
 LOCAL v AS VARIANT
 v = b
 ? STR$(VARIANTVT(v)) 'wrong, 3 returned,long integer

 v = b AS BYTE '<------ AS works
 ? STR$(VARIANTVT(v)) 'correct, 17 byte unsigned
END FUNCTION

v = b? 'is also wrong, 3 returned, long integer

[Dale Yarker]

from Help for LET statement (with Variants) -

LET VrntVar= expression [AS vartype]

"The numeric or string expression is evaluated, and the result is stored in the variant variable. PowerBASIC will choose an appropriate numeric or string data type to use. However, you can specify a preferred format by adding an optional AS vartype clause. This can be BYTE, WORD, DWORD, INTEGER, LONG, QUAD, SINGLE, DOUBLE, CURRENCY, or WSTRING. Strings in a variant are always stored in wide Unicode, regardless of whether you add AS WSTRING or not. PowerBASIC handles the conversion automatically, if it is needed. . . ." (bold added)

Apparently PB picks type unless you force with AS

Cheers,

[Michael Mattias]

If you are not comfy with allowing PB to make the assignment of the variant datatype, or if PB does not support the variant datatype required*, here is how to do it..

Create VT_DATE variant Datatype 9-14-09

This function may also come in handy..

Get VARIANTVT literal


* I ran into this when I needed both VT_DATE and VT_BOOL types, which are not supported by PB.. and on the "read me" types, the VARIANT(type specifier) does not read these or the VT_DECIMAL type.

FWIW, VT_DATE is needed to pass parameters to prepared SQL queries; VT_BOOL is required by some of the MQ interfaces (PB COM browser creates these as "LONG") and VT_DECIMAL is returned by some SQL queries from Oracle DBs (maybe more but Oracle for sure).

[Mike Doty]

Thanks Michael for all the return values, but BYTE still returns 3 instead of 17 using VARIANTVT.

#DIM ALL
FUNCTION PBMAIN AS LONG
 LOCAL b  AS BYTE
 LOCAL vW AS VARIANT
 LOCAL iType AS LONG
 vW = b
 iType =   VARIANTVT(vW)
 ? variantTypeLiteral(iType)
END FUNCTION

FUNCTION VariantTypeLiteral ( BYVAL iType AS LONG) AS STRING

    LOCAL X  AS LONG, W AS STRING

    ' mask off the array, BYREF and vector bits , handle separately
     X = iType AND NOT(%VT_ARRAY OR %VT_BYREF OR %VT_VECTOR)

    SELECT CASE AS LONG X
          CASE   %VT_EMPTY      :  W = "VT_EMPTY"      '  0 no value of any kind
          CASE   %VT_NULL       :  W = "VT_NULL"       '  1 null (eg from database)
          CASE   %VT_I2         :  W = "VT_I2"         '  2 INTEGER
          CASE   %VT_I4         :  W = "VT_I4"         '  3 LONG
          CASE   %VT_R4         :  W = "VT_R4"         '  4 single
          CASE   %VT_R8         :  W =  "VT_R8"        '  5 double
          CASE   %VT_CY         :  W = "VT_CY"         '  6 Currency
          CASE   %VT_DATE       :  W = "VT_DATE"       '  7 date (a double =   ccyymmdd.hhmmsstt)
          CASE   %VT_BSTR       :  W = "VT_BSTR"       '  8 dynamic string
          CASE   %VT_DISPATCH   :  W = "VT_DISPATCH"   '  9 IDispatch
          CASE   %VT_ERROR      :  W =  "VT_ERROR"     ' 10 errror (eg DISP_E_PARAMNOTFOUND)
          CASE   %VT_BOOL       :  W = "VT_BOOL"       ' 11 Boolean
          CASE   %VT_VARIANT    :  W =  "VT_VARIANT"   ' 12 Variant
          CASE   %VT_UNKNOWN    :  W = "VT_UNKNOWN"    ' 13  IUnknown (interface)
          CASE   %VT_DECIMAL    :  W = "VT_DECIMAL"    ' 14   decimal 16-byte fixed point use VarBstrfromDec to convert.
          CASE   %VT_I1         :  W  = "VT_I1"        ' 16  byte (signed)
          CASE   %VT_UI1        :  W = "VT_UI1"        ' 17  byte (unsigned)
          CASE   %VT_UI2        :  W = "VT_UI2"        ' 18  WORD  (unsigned)
          CASE   %VT_UI4        :  W = "VT_UI4"        ' 19  DWORD (unsigned)
          CASE   %VT_I8         :  W = "VT_I8"         ' 20   QUAD (signed)
          CASE   %VT_UI8        :  W = "VT_UI8"        ' 21  QUAD (unsigned) (LARGE_UINT)
          CASE   %VT_INT        :  W = "VT_INT"        ' 22  integer (signed)
          CASE   %VT_UINT       :  W = "VT_UINT"       ' 23  WORDr (unsigned)
          CASE   %VT_VOID       :  W = "VT_VOID"       ' 24  C-style VOID (???)
          CASE   %VT_HRESULT    :  W = "VT_HRESULT"    ' 25  COM result code
          CASE   %VT_PTR        :  W = "VT_PTR"        ' 26  Pointer
          CASE   %VT_SAFEARRAY  :  W = "VT_SAFEARRAY"  ' 27  VB array
          CASE   %VT_CARRAY     :  W = "VT_VCARRAY"    ' 28  C-style array
          CASE   %VT_USERDEFINED:  W = "VT_USERDEFINED"' 29  user-defined type
          CASE   %VT_LPSTR     :  W = "VT_LPSTR"       ' 30  (ptr to)  ANSI STRING (ASCIIZ PTR)
          CASE   %VT_LPWSTR      :  W = "VT_LPWSTR"    ' 31  (ptr to)  Unicode string
          CASE   %VT_FILETIME     :  W = "VT_FILETIME  ' 64  FILETIME structure
          CASE   %VT_BLOB       :  W = "VT_BLOB"      '  64  arbitrary block of memory
          CASE   %VT_STREAM     :  W = "VT_STREAM"     ' 66  byte stream
          CASE   %VT_STORAGE   :  W = "VT_STORAGE"     ' 67  Name of the storage object
          CASE   %VT_STREAMED_OBJECT: :  W = "VT_STREAMED_OBJECT"  ' 68 A stream that contains an object
          CASE   %VT_STORED_OBJECT: :  W = "VT_STORED_OBJECT"  ' 69  A storage object
          CASE   %VT_BLOB_OBJECT: :  W = "VT_BLOB_OBJECT"  ' 70 A block of memory that represents an object
          CASE   %VT_CF           :  W = "VT_CF"        ' 71 A clipboard format
          CASE   %VT_CLSID        :  W = "VT_CLSID"        ' 72 Class ID
          CASE   ELSE             :  W = USING$ ("Unrecognized &", HEX$(X,2))
    END SELECT

    ' add literals for optional bits in an order which makes sense when reading them
    IF ISTRUE (iType AND %VT_BYREF) THEN
        W  =   W & " BYREF"
    END IF
    IF ISTRUE (iType AND %VT_VECTOR) THEN
          W = W & " VECTOR (leading count)"
    END IF
    IF ISTRUE (Itype AND %VT_ARRAY) THEN
          W =  W & " ARRAY
    END IF

    FUNCTION = W

END FUNCTION'

[Dale Yarker]

. . . , but BYTE still returns 3 instead of 17 using VARIANTVT.

Because you're still not using AS BYTE

like
vW = b AS BYTE
in your code. Not to be confused with
LOCAL b AS BYTE

[Mike Doty]

Doh

And it now returns the correct result with Michaels routine.
W = "17 VT_UI1" ' 17 byte (unsigned)