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cannot convert from 'char *' to 'char'

Posted on 2004-08-24
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Last Modified: 2010-04-01
With code below, i got error C2440: '=' : cannot convert from 'char *' to 'char'.
What do i did wrong?

char *StreamClient(char *streamServer, short portNumber, long UserId, char Type[3])
{
      ...
      return response;      //response is a char[10]
}

STDMETHODIMP CCom::Add(LONG UserId, char *Result)
{
      AFX_MANAGE_STATE(AfxGetStaticModuleState());

      OpenConn();
      *Result=StreamClient(SERVERNAME, SERVERPORT, UserId, "ADD");
      WSACleanup();
      CloseConn();

      return S_OK;
}
0
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Question by:mammouth
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5 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 125 total points
ID: 11886919
Shouldn't that be

STDMETHODIMP CCom::Add(LONG UserId, char **Result) // <---- !
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());

    OpenConn();
    *Result=StreamClient(SERVERNAME, SERVERPORT, UserId, "ADD");
    WSACleanup();
    CloseConn();

    return S_OK;
}

?
0
 
LVL 15

Expert Comment

by:efn
ID: 11886946
StreamClient returns a pointer to char.  Result is a pointer to char, so *Result is a char.  The compiler should be happy if you assign the value returned from StreamClient to Result instead of *Result.

But jkr's solution is more likely to be useful.

--efn
0
 
LVL 86

Expert Comment

by:jkr
ID: 11886949
Or

STDMETHODIMP CCom::Add(LONG UserId, char *Result)
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());

    char* tmp;
    OpenConn();
    tmp=StreamClient(SERVERNAME, SERVERPORT, UserId, "ADD");
    strcpy(Result,tmp);
    WSACleanup();
    CloseConn();

    return S_OK;
}
0
 
LVL 23

Expert Comment

by:Mysidia
ID: 11886983
StreamClient returns a char*  (Pointer to a character)

and Result is declared as char* (Pointer to a character)

The dereferenced thing *Result is just a character.

So when you assign the character to the result of StreamClient (which is a pointer to a character):
the types are incompatible

The result parameter would need to be of type char**  instead

(or StreamClient needs to return a char type instead of a char*)
0
 
LVL 1

Author Comment

by:mammouth
ID: 11891732
When i do any of jkr solution, i got error.

f:\VSDotNet\Vc7\atlmfc\include\atlcom.h(1759): error C2259: 'ATL::CComObject<Base>' : cannot instantiate abstract class
        with
        [
            Base=CCom
        ]


//com.cpp file
STDMETHODIMP CCom::Add(LONG UserId, char **Result) // <---- !
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());

    OpenConn();
    *Result=StreamClient(SERVERNAME, SERVERPORT, UserId, "ADD");
    WSACleanup();
    CloseConn();

    return S_OK;
}

//.idl file
[id(1), helpstring("method Add")] HRESULT Add([in] LONG UserId, [out,retval] char **Result);

//.h file
STDMETHOD(Add)(LONG UserId, char **Result);


What's wrong?
note: Before i used Result as a CHAR, it were a LONG.

Thankx
0

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