return string from COM method

i try to make dll and install it under "Component Services".
i tried to make method that return string but when i test it i don't get any result

Code:

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STDMETHODIMP CSimpleChat::CellMe(BSTR name, BSTR** helloMessage)
{

        CString temp = _T("Hi ");
    temp += name;
    temp += ", welcome to the simple chat server!";
    BSTR str = temp.AllocSysString();
    *helloMessage = &str;
        return S_OK;
}

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thanks for the help i am new to this.

Quote:

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Originally Posted by wanttolearn1

i try to make dll and install it under "Component Services".
i tried to make method that return string but when i test it i don't get any result

Code:

---

STDMETHODIMP CSimpleChat::CellMe(BSTR name, BSTR** helloMessage)
{
        ...
        return S_OK;
}

---

---

Are you sure you want BSTR** type for the _out_ parameter, not a BSTR* one?

i also tried

Code:

---

STDMETHODIMP CSimplec1::CellOut1(BSTR name1, BSTR* ret)
{
        // TODO: Add your implementation code here
        CString temp = _T("Hi ");
    temp += name1;
    temp += ", welcome to the simple chat server!";
    BSTR str = temp.AllocSysString();
    *ret = str;
        ::SysFreeString(str);
        return S_OK;
}

---

same problem

i found the problem, its because of
::SysFreeString(str);
what is the correct way to do it?

Quote:

---

Originally Posted by wanttolearn1

i also tried

Code:

---

STDMETHODIMP CSimplec1::CellOut1(BSTR name1, BSTR* ret)
{
        // TODO: Add your implementation code here
        CString temp = _T("Hi ");
    temp += name1;
    temp += ", welcome to the simple chat server!";
    BSTR str = temp.AllocSysString();
    *ret = str;
        ::SysFreeString(str);
        return S_OK;
}

---

same problem

---

First replace

Code:

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    *ret = str;

---

with

Code:

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    ret = &str;

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Then remove the ::SysFreeString(str); call because after it is done there is no any data in str.
The ::SysFreeString must be called by the caller of your CellOut1 method.

Quote:

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Originally Posted by VictorN

The ::SysFreeString must be called by the caller of your CellOut1 method.

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how do i do this?
if for example i call the method from vbscript?
i need to call to another method to clear "str" variable?
isn't there a better way?

Quote:

---

Originally Posted by wanttolearn1

how do i do this?
if for example i call the method from vbscript?
i need to call to another method to clear "str" variable?
isn't there a better way?

---

It's not you to do this. Out value ownership is on client side, so client is responsible for freeing the string. In your case this is vbscript.

PS. You definitely need to get some very basic reading on COM model.

Quote:

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Originally Posted by Igor Vartanov

It's not you to do this. Out value ownership is on client side, so client is responsible for freeing the string. In your case this is vbscript.

PS. You definitely need to get some very basic reading on COM model.

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any recommended articles?

Inside Com (Microsoft Programming Series)