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Hi
I want to pass a member function to the std::for_each algorithm but strguggling. I've seen where you can use std::mem_fun to bind a member function of the 'contained' class, but I want a member function of a different class...code below shows what I want to do and code after that shows my work around.
I could use a for..next loop, but don't think I should when these algorithms are so d*** neat!
What I want to do....
class myClass
{
private:
void DoSomethingWithString( std::string *pString );
public:
void Go()
{
std::set <std::string > myStrings;
myStrings.insert("ABC");
myStrings.insert("DEF");
myStrings.insert("GHI");
std::for_each(myStrings.begin() , myStrings.end() , );
}
};
and a work around....
class myClass
{
class DoStringThing
{
private:
myClass* m_class;
public:
DoStringThing( myClass* class_param) : m_class( class_param)
{
}
void operator()( std::string &filename)
{
m_class->DoSomethingWithString( &filename );
}
};
friend class DoStringThing;
private:
void DoSomethingWithString( std::string *pString );
public:
void Go()
{
std::set <std::string> myStrings;
myStrings.insert("ABC");
myStrings.insert("DEF");
myStrings.insert("GHI");
std::for_each(myStrings.begin() , myStrings.end() , DoStringThing(this) );
}
};
So, how can I call a member of the class that is executing the for_each...?
Regards
![Rose | [Rose]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/rose.gif) Angel
*********************************************
The sooner you fall behind, the longer you have to catch up.
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Correct. Function object is a good solution in this example.
Kuphryn
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Hi - thanks for the answer. I really want to know how to call a member function instead of using a functor.
Is it possible?
Cheers
Regards
Angel
*********************************************
The sooner you fall behind, the longer you have to catch up.
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There are more elegant solutions with function objects.
Kuphryn
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Yes, I know, but I would still like to now how to use a member function....
Regards
Angel
*********************************************
The sooner you fall behind, the longer you have to catch up.
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Definitely! Update when you figure out the solution without overloaded operator().
Kuphryn
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Also, there is bind2nd().
Kuphryn
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Hello Angel1058,
One way you can achieve the use of a member function is to declare a class deriving from std::string :
class MyString : public std::string
{
public :
MyString()
{
}
MyString(const char* pstring) :
std::string(pstring)
{
}
~MyString()
{
}
void DoSomethingWithString()
{
std::cout << c_str() << std::endl;
}
};
Yes, you basically extend the std::string with a public member function named DoSomethingWithString().
Then in myClass::Go(), you use MyString instead of std::string :
void Go()
{
std::set<MyString> myStrings;
myStrings.insert("ABC");
myStrings.insert("DEF");
myStrings.insert("GHI");
std::for_each
(
myStrings.begin(),
myStrings.end(),
mem_fun_ref(&MyString::DoSomethingWithString)
);
}
Yes, you would have seen it by now, use mem_fun_ref() as the predicate for for_each(). Basically, MyString::DoSomethingWithString() wsill be called on each contained object in myStrings (which is a set of MyString objects).
Give it a try.
Best Regards,
Bio.
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Not meaning to sound ungrateful, I am grateful, always for the time CPians give, but I don't want to call a member of the contained object. I don't want to use a functor. I don't want to use a static member function. I want to use a member of the class that invokes the for_each.
class MyClass
{
public:
void DoSomethingWithString( std::String *ptrToString()
{std::cout << ptrToString;}
void LookThroughContainer( std::vector &c)
{
for_each(c.begin() , c.end() , );
}
};
Just call the MyClass::DoSomethingWithString member for each element in a container from MyClass::LookThroughContainer. I *KNOW* this isn't the best way to do this, functors are, but I want to know a) IF you can do it and b) HOW you can do it.
Thanks again for all your time
Regards
Angel
*********************************************
The sooner you fall behind, the longer you have to catch up.
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Try this:
std::bind1st(std::mem_fun1(&myClass::DoSomethingWithString), this)
mem_fun1 is no longer part of the C++ standard (it's old school) but if you're using an old compiler/STL (like MSVC6) you'll have to use it to get it to work. Most new environments provide it for backwards compatibility.
I think you'll have to remove the private on the DoSomethingWithString function. I can think of a workaround for this is it offends you but I'm not sure it's worth the effort.
Steve
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Finally  !!! Many thanks. I thought I had tried most combinations of bind1st / Bind2nd with mem_fun / mem_fun1, but clearly not. I appreciate your time.
Regards
Angel
*********************************************
The sooner you fall behind, the longer you have to catch up.
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Steve,
I am trying to do something very similar, but I cannot get your sample to compile. I have boost, so there may be a better way to do this, but basically I am trying to do the same thing - i.e. use some variant of bind to call a member function of the class that is calling for_each, e.g.:
class CTest
{
public:
void SomeFunc(const std::wstring& str) const
{
}
void DoSomething(void) const
{
std::vector<std::wstring> v;
v.push_back(L"test");
...
for_each(v.begin(), v.end(), std::bind1st(std::mem_fun1(&CTest::SomeFunc), this));
}
Any hints before my head explodes? 
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There's nothing wrong with your code, which makes me think you're using MVSC6 - It's your compiler. On a real compiler your code will work. To make it work form MSVC6 change SomeFunc so it returns something. i.e.
bool SomeFunc(const std::wstring& str) const
{
return true;
}
The flaw in MSVC6 is illustrated below:
void ReturnsVoid() {}
void CallsReturnsVoid()
{
return ReturnsVoid();
}
This code should compile - A void function can't return with return void; but it should be able to return with return ReturnsVoid();.
This feature is very important when writing generic functions with templates.
Steve
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Steve,
I am actually using Visual Studio 2005 - so have MSC8 (with an STL that I thought was meant to be pretty good!).
Either way - with or without returning something - the code still won't compile.
Here it is in full:
#include "stdafx.h"
#include <windows.h>
#include <string>
#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>
class CTest
{
public:
void SomeFunc(const std::wstring& str) const
{
OutputDebugString(str.c_str());
}
void DoSomething(void) const
{
std::vector<std::wstring> v;
v.push_back(L"test");
for_each(v.begin(), v.end(), std::bind1st(std::mem_fun1(&CTest::SomeFunc), this));
}
};
int _tmain(int argc, _TCHAR* argv[])
{
CTest test;
test.DoSomething();
return 0;
}
When I compile this, I get the following error:
error C2782: 'std::mem_fun1_t<_Result,_Ty,_Arg> std::mem_fun1(_Result (__thiscall _Ty::* )(_Arg))' : template parameter '_Ty' is ambiguous
c:\program files\microsoft visual studio 8\vc\include\functional(604) : see declaration of 'std::mem_fun1'
could be 'const CTest'
or 'CTest'
If I remove 'const' from the two methods, I get lots of different errors. Head meet brick wall.
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Steve,
Thanks to the boost list and Stuart Dootson, I have a solution using boost::bind:
for_each(v.begin(), v.end(), bind(&CTest::SomeFunc, this, _1));
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I want to pass my own information to propertypage that is created by propertysheet using "AddPage"&"Create".
But I found the fild "lParam" in m_psp has been used by WTL for core wrapp
Is there any method I can pass my own info to propertypage when they are created, initialize before shown.
-- modified at 9:20 Friday 10th March, 2006
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Hello,
I was wondering if it is possible to implement MDI in a MFC based ActiveX control. I was able to implement SDI (using a sample from MSDN), but I faced some difficulties when implementing MDI. Any help would be highly appreciated.
Thanks in advance,
Dennis.
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Disable "Minimize CRT use in ATL" in your project properties, and it should work.
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Thanks a lot! That's really fantastic.
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Does any one know how to make modeless dlgs/propertysheets destroy by themself?
my code:
<br />
pdlg = new CMyDlg;<br />
if(pdlg && pdlg->Create(hwndParent))<br />
pdlg->ShowWindow(SW_SHOW);<br />
<br />
void OnClose(UINT uCode, int nID, HWND hwndCtrl)
{<br />
DestroyWindow();<br />
}<br />
void OnNcDestory(void)<br />
{<br />
m_hWnd = NULL;<br />
delete this;
}<br />
But it works fine in MFC
http://www.codeproject.com/dialog/gettingmodeless.asp[^]
any idea?
-- modified at 10:34 Thursday 9th March, 2006
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