Passing a function name as a paramter to a template function

Question

5.00/5 (1 vote)

See more:

Is is possible to pass a function name as a parameter to a template using C++/CLI

I want to use a template function to do some validation where the first parameter will be a string or integer, the second and third will always be dates in string format and the third a fuction name. The parameters will be operated on and the result passed into the function supplied as a paramenter.

This validation function will be accessed throughout my system and where it is called from will dictate the function name passed in.

This is the my first opportunity to apply a template in a real world scenario, so very excited by the possibilities presented.

I will gladly accept suggestions with either a C++/CLI or C# orientation and translate any C# myself.

Posted 27-Jan-11 22:14pm

Ger Hayden

Updated 27-Jan-11 23:18pm

v4

Add a Solution

Comments

Manas Bhardwaj 28-Jan-11 4:19am

removed c# tag

ARopo 28-Jan-11 5:00am

Not sure what exactly it is you want to do. do you want to write a template class, a template function or something else? You might be better just trying it and then posting the code if there is a problem with it.

2 solutions

Solution 2

OK, forgive the naming convention - I'll update it later, but so far this is what I've got, and I am confident it will give me what I want when used in a template:

.h

delegate bool DateDelegate(MySqlConnection^, String^, String^, String^, int);
    int Check_Date(DateDelegate^ x,MySqlConnection^, String^, String^, String^, int);

then in the .cpp

DateDelegate^ dtDel;
dtDel = gcnew DateDelegate(&CComs_UM::CheckExists_UserMaster);
Check_Date(dtDel,
           m_LocalConnection,
           m_OrigUsername,
           nullptr,
           nullptr,
           0);

:
:
int User::frmUserMaster::Check_Date(DateDelegate^ x,MySqlConnection^ a1, String^ a2, String^ a3, String^ a4, int a5 )
{
    x->Invoke(a1,a2,a3,a4,a5);
    return 0;
}

Posted 28-Jan-11 8:16am

Ger Hayden

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Accepted Answer · 2011-01-27T23:09:00

Solution 1

Function names in C/C++ are actually function pointers. And yes, of course, you may pass a function pointer to a template function.
:)

Posted 27-Jan-11 23:09pm

CPallini

Comments

ARopo 28-Jan-11 5:23am

You can pass function pointer to any function template or not. But not as a template parameter(this should be a type could be a type of function pointer) template parameters being the ones in angle brackets <t1, t2=""> as opposed to function parameters in normal brackets (T1 arg1,T2 arg3)

CPallini 28-Jan-11 5:45am

Of course I intended it as (template) function argument. Anyway, you're wrong, try:

#include <iostream>
#include <string>

using namespace std;

void show(string s)
{
cout << "foo" << endl;
}

typedef void (*PUNARYFUN)(string s);

template <PUNARYFUN p>
void _apply(string s)
{
p(s);
}

int main()
{
_apply<show>(string("foo"));
}

ARopo 28-Jan-11 6:33am

Oh year, thanks for the code you learn something everyday. +5 for the comment

Ger Hayden 28-Jan-11 7:05am

Will give this a shot this afternoon

Espen Harlinn 28-Jan-11 13:50pm

5+ and it gets even better with template metaprogramming/c++ template polymorphism http://en.wikipedia.org/wiki/Template_metaprogramming