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kanam
Guest
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 Posted: Wed Aug 18, 2004 12:13 pm Post subject: What's different? (empty interface inheritance) |
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i want to use class member function pointer.
i did as below case. but this program terminates with runtime error.
interface ICtlBase
{
virtual ~ICtlBase(){};
virtual void SetName(CString strData) = 0;
virtual void SetID(CString strData) = 0;
};
class CCtlBase : public ICtlBase
{
public:
virtual ~CCtlBase();
virtual void SetName(CString strData);
virtual void SetID(CString strData);
typedef void (CCtlBase::*SetFunction)(CString);
void ExeFunc(SetFunction);
};
void CCtlBase::ExeFunc(SetFunction func)
{
SetFunction setFunction = func;
this->*setFunction("aaaa");
}
class CCtlEdit : public CEdit, public CCtlBase
{
public:
virtual ~CCtlEdit();
virtual void SetText(CString strText);
void Test();
};
void CCtlEdit ::Test()
{
ExeFunc(SetText);
}
when this program run CCtlEdit::Test, this program terminate with runtime error.
but i modified this program as below.
interface IBase // empty interface
{
};
interface ICtlBase : public IBase
{
virtual ~ICtlBase(){};
virtual void SetName(CString strData) = 0;
virtual void SetID(CString strData) = 0;
};
To my surprise, modified program work well.
only ICtlBase inherits empty interface IBase.
What happened?
please Let me know this situation.
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Victor Bazarov
Guest
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| Posted: Wed Aug 18, 2004 6:37 pm Post subject: Re: What's different? (empty interface inheritance) |
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kanam wrote:
| Quote: | i want to use class member function pointer.
i did as below case. but this program terminates with runtime error.
interface ICtlBase
|
Are you in the right newsgroup? Last time I checked 'interface'
wasn't part of C++... Did you mean 'struct'?
OK, I'll assume
#define interface struct
for the duration of this thread.
| Quote: | {
virtual ~ICtlBase(){};
virtual void SetName(CString strData) = 0;
|
'CString' is undefined. Now I am fairly certain you're in a wrong
newsgroup. For now I'll assume
#define CString std::string
(and the appropriate headers included)
| Quote: | virtual void SetID(CString strData) = 0;
};
class CCtlBase : public ICtlBase
{
public:
virtual ~CCtlBase();
virtual void SetName(CString strData);
virtual void SetID(CString strData);
typedef void (CCtlBase::*SetFunction)(CString);
void ExeFunc(SetFunction);
};
void CCtlBase::ExeFunc(SetFunction func)
{
SetFunction setFunction = func;
this->*setFunction("aaaa");
|
This is unnecessary. You could simply say
(this->*func)("aaaa");
| Quote: | }
class CCtlEdit : public CEdit, public CCtlBase
|
'CEdit' is undefined here.
| Quote: | {
public:
virtual ~CCtlEdit();
virtual void SetText(CString strText);
void Test();
};
void CCtlEdit ::Test()
{
ExeFunc(SetText);
|
'ExeFunc' expects a pointer to a member of CCtlBase. There is no member
function named 'SetText' in CCtlBase. You could only call 'ExeFunc' with
'SetName' or 'SetID' without a cast. You _could_ call it with 'SetText',
but you need a static_cast here:
ExeFunc(static_cast<SetFunction>(&CCtlEdit::SetText));
| Quote: | }
when this program run CCtlEdit::Test, this program terminate with runtime error.
but i modified this program as below.
interface IBase // empty interface
{
};
interface ICtlBase : public IBase
{
virtual ~ICtlBase(){};
virtual void SetName(CString strData) = 0;
virtual void SetID(CString strData) = 0;
};
To my surprise, modified program work well.
only ICtlBase inherits empty interface IBase.
What happened?
|
I have no idea. I fixed your program as little as I deemed necessary,
here is the working solution:
-------------------------------------
#include <string>
#include <iostream>
using namespace std;
#define interface struct
#define CString string
interface ICtlBase
{
virtual ~ICtlBase() {}
virtual void SetName(CString strData) = 0;
virtual void SetID(CString strData) = 0;
};
class CCtlBase : public ICtlBase
{
public:
virtual ~CCtlBase() {}
virtual void SetName(CString strData)
{cout << "Name: " << strData << endl;}
virtual void SetID(CString strData)
{cout << "ID: " << strData << endl;}
typedef void (CCtlBase::*SetFunction)(CString);
void ExeFunc(SetFunction);
};
void CCtlBase::ExeFunc(SetFunction func)
{
(this->*func)("aaaa");
}
class CCtlEdit : public CCtlBase
{
public:
virtual ~CCtlEdit() {}
virtual void SetText(CString strText)
{cout << "Text: " << strText << endl;}
void Test();
};
void CCtlEdit ::Test()
{
ExeFunc(static_cast
}
int main()
{
CCtlEdit e;
e.Test();
}
---------------------------------------------------------
Victor
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]
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