Does clarion have a variant type?
Hi andrew, were can we get a copy of your ado classes, to start adding our
own stuff.
are you ready to sell this class wrapper
im sure were all prepared to buy a copy it !
the problems with products like calling the explorer ocx are well documented
, (simon burrows) ect.
cheers steve ryan
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> Hi Allen,
> > Does clarion have a variant type?
> Just treat is as a group and pass by address. Where you need to pass by
value, I have some Asm code that puts a whole in the
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> stack and pushes the data on so those methods can be called. Attached is
code, below example etc..
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> The following example calls the ADO Recordset Seek method. This is because
you can't simply push it in a thread safe way any
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> other way and you need to use the group rather than the built in type so
you have the control you need without the datatype
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> conversion code in the RTL getting in the way. The tVariant structure can
be found in the ai_comdef.inc file. A brief
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> explanation of the structures follows the example....
> CRecordSet21.Seek procedure(*tVariant vtKeyValues, long SeekOption)
> Offs long
> hr HRESULT
> pFunc long
> pRst long
> code
> pFunc = address(self.IRst21.raw_Seek)
> pRst = address(self.IRst21)
> Offs = PushLong(Offs, SeekOption)
> Offs = PushVariant(Offs, address(vtKeyValues))
> Offs = PushLong(Offs, pRst)
> hr = AdjustStackCallAndClean(Offs, pFunc)
> return hr
> The srVal over iVal is needed for 4 byte real values coming back from
something like ADO else the value gets messed up. See the
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> next explanation. iVal recieves all values of a 4 byte size such as
VT_BSTR, VT_I4 etc. BSTR values are pointers and need
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> converting to clarion cstrings using API functions.
> tVariant group,type
> vt short
> wReserved1 short
> wReserved2 short
> wReserved3 short
> iVal long
> iVal2 long
> srVal sreal,over(iVal)
> end
> This is a variation of the tVariant specifically for a real as this is
needed when reading real values into a variant from
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> something like ADO or clarion will use it's type conversion and mess up
the value.
> tVariantr group,type
> vt short
> wReserved1 short
> wReserved2 short
> wReserved3 short
> rVal real
> end
> The following is needed for omitable params, nothing else will do less you
receive an error.
> vtMissing group
> vt short(VT_ERROR)
> wReserved1 short
> wReserved2 short
> wReserved3 short
> iVal long(DISP_E_PARAMNOTFOUND)
> pad long
> end
> Here's how to compile in the ASM code...
> SupFnc class,link('supfnc.a', _COMLinkMode_),dll(_COMDllMode_)
> end
> module('supfnc.a')
> AdjustStackCallAndClean(long dwSize, long
pFunc),long,name('_AdjustStackCallAndClean')
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> PushLong(long Offs, long iVal),long,name('_PushLong')
> PushVariant(long Offs, long pvt),long,name('_PushVariant')
> end
> Only functions that pass them by value need this, all others I have
encountered in COM do not need anything special doing. But
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> if it is needed, all params must be pushed this way. Thankfully they are
all either longs or variants. It's a quick dirty hack
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> but works nonetheless.
> Let me know if you need any more help. On this NG rather than email would
be better so other people can learn also.
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> HTH
> Regards
> Andy Ireland
> [Plugware Solutions.com Ltd]
> [Tel : +44 1249 813335]
> [Fax : +44 1249 813462]
