_variant_t to CString

CPallini

I suppose you need the string representation of the _variant_t value. You've to properly format a CString object, depending on the value of the vt member of the encapsulated VARIANT struct. For instance

CString str;
_variant_t v1;

v1 = 0.53;

switch (v1.vt)
{
//...
case VT_R8:
str.Format(_T("%g"), v1.dblVal);
break;
//...
}

MessageBox(str, _T("Variant value"));

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Stuart Dootson

In VS2008, this should do the job...

_variant_t v;
// Set a value in v
CString s = v;

CString has assignment operator and constructor overl;oads that take a const VARIANT&. _variant_t has an extrractor that returns a VARIANT.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Stuart Dootson

Noooooo - you don't need to bother with that - there's a VariantChangeType function that'll do that for you when you convert a VARIANT to a BSTR. And even more conveniently, the combination of _variant_t extractor operators and CString constructors will do all that for you. A simple assignment of _variant_t to CString is all that's needed...

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

rdop

Thanks for responce.I hava a biray type data in _variant_t. _variant_t v1; v1=(54 '6',53 '5',52 '4',54 '6',52 '4',0,0,0,0,0,0,0,0,0,0,0,0,0,0,0); Can i convert these values in CString or not. Origal values is"65464". Plz help me

rdop

Plz help me some one

Lost User

Hi rdop, The following snippit will work on all Microsoft compilers:_variant_t v; v = 3.141; ::VariantChangeType(&v, &v, 0, VT_BSTR); CString s = (LPTSTR)(_bstr_t)v.bstrVal;
Best Wishes, -David Delaune

Stuart Dootson

I (and Microsoft, who wrote the _variant_t and CString code) have helped you - you just assign the _variant_t to the CString - what more do you want?!?!?!?!?

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

CPallini

Nice to know :thumbsup:. What about _variant_t containing arrays? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

rdop

See what happen.

_variant_t vtValue;
vtValue = m_pRset->Fields->GetItem("Bianry")->GetValue();
CString b=vtValue;
output is b = "??4"
when i copy the vtValues at the time of debug then i got values
safearray of UI1 = [20](54 '6',53 '5',52 '4',54 '6',52 '4',0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)

Any more information if you nedd then i will give you.

CPallini

What is v1.vt value? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Stuart Dootson

As it's an array, VariantChangeType's not going to work. So, I'd suggest the code below. I'm assuming you want to access the non-null characters of the array and make them into a string?

CComSafeArray<char, VT_UI1> sa(V_ARRAY(&v));
CString s;
for(int index=sa.GetLowerBound();index<=sa.GetUpperBound()&&sa[index];++index)
{
s+=sa[index];
}

[edit] You'll also need to #include atlsafe.h and oleauto.h [/edit]

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Stuart Dootson

CPallini wrote:

What about _variant_t containing arrays?

Use CComSafeArray[^].

_variant_t v;
// Assign a SAFEARRAY value to v
CComSafeArray<char, VT_UI1> sa(V_ARRAY(&v));
// Now we can access the SAFEARRAY using sa.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Lost User

Hi Stuart, What do you think about this VT_UI1 SAFEARRAY to CStringA conversion method?BSTR b; BstrFromVector(pSA,&b); CStringA s = (LPCSTR)b;
Best Wishes, -David Delaune

Stuart Dootson

New to me - that'll teach me to do what I've told many other people to do and read the documentation :laugh: And of course it'll work with wide CStrings as well.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

rdop

thanks it's working for me.