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  4. _variant_t to CString

_variant_t to CString

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  • R rdop

    Hi All How can i convert _variant_t to CString?

    S Offline
    S Offline
    Stuart Dootson
    wrote on last edited by
    #3

    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

    R 1 Reply Last reply
    0
    • C 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]

      S Offline
      S Offline
      Stuart Dootson
      wrote on last edited by
      #4

      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

      C 1 Reply Last reply
      0
      • C 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]

        R Offline
        R Offline
        rdop
        wrote on last edited by
        #5

        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

        C 1 Reply Last reply
        0
        • S 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

          R Offline
          R Offline
          rdop
          wrote on last edited by
          #6

          Plz help me some one

          S 1 Reply Last reply
          0
          • R rdop

            Hi All How can i convert _variant_t to CString?

            L Offline
            L Offline
            Lost User
            wrote on last edited by
            #7

            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

            1 Reply Last reply
            0
            • R rdop

              Plz help me some one

              S Offline
              S Offline
              Stuart Dootson
              wrote on last edited by
              #8

              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

              R 1 Reply Last reply
              0
              • S 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

                C Offline
                C Offline
                CPallini
                wrote on last edited by
                #9

                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]

                S 1 Reply Last reply
                0
                • S 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

                  R Offline
                  R Offline
                  rdop
                  wrote on last edited by
                  #10

                  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.

                  S 1 Reply Last reply
                  0
                  • R 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

                    C Offline
                    C Offline
                    CPallini
                    wrote on last edited by
                    #11

                    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]

                    1 Reply Last reply
                    0
                    • R 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.

                      S Offline
                      S Offline
                      Stuart Dootson
                      wrote on last edited by
                      #12

                      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

                      L R 2 Replies Last reply
                      0
                      • C 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]

                        S Offline
                        S Offline
                        Stuart Dootson
                        wrote on last edited by
                        #13

                        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

                        1 Reply Last reply
                        0
                        • S 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

                          L Offline
                          L Offline
                          Lost User
                          wrote on last edited by
                          #14

                          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

                          S 1 Reply Last reply
                          0
                          • L 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

                            S Offline
                            S Offline
                            Stuart Dootson
                            wrote on last edited by
                            #15

                            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

                            1 Reply Last reply
                            0
                            • S 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

                              R Offline
                              R Offline
                              rdop
                              wrote on last edited by
                              #16

                              thanks it's working for me.

                              1 Reply Last reply
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