Re: How to invoke the methods of an object selecting them from a table

From:
Sam <sam@email-scan.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 05 Feb 2008 06:10:58 -0600
Message-ID:
<cone.1202213457.620182.28765.500@commodore.email-scan.com>
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Stefano Sabatini writes:

This is my solution for subject:

#include <string>
#include <iostream>

using namespace std;

class DumbThing {
public:
    void sayFoo() { cout << "Foo!" << endl; }

    static void sayFoo(DumbThing &t) {
        t.sayFoo();
    }

    void sayBar() { cout << "Bar!" << endl; }

    static void sayBar(DumbThing &t) {
        t.sayBar();
    }
};

struct ClassMethod {
    string name;
    void (*method)(DumbThing &);
};

int main(void) {
    
    struct ClassMethod DumbThingMethods[] = {
        { "sayFoo", &DumbThing::sayFoo },
        { "sayBar", &DumbThing::sayBar }
    };

    int DumbThingMethodsNum = sizeof(DumbThingMethods) / sizeof(ClassMethod);

    DumbThing t;
    for (int i=0; i < DumbThingMethodsNum; i++)
        DumbThingMethods[i].method(t);

    return 0;
}

The problem with this solution is that I have to create for each
method a corresponding static function, can you contrive a solution
which doesn't require this?

Many thanks in advance for any advice.


You want to use class member pointers:

// Declare:

class Foo {

public:
    void x();
    void y();
};

// Don't use arrays, when you really want a map:

std::map<std::string, void (Foo::*)() > methods;

// Initialize:

methods["x"]= &Foo:x;
methods["y"]= &Foo:y;

// Invoke some method on an object.

void callFoo(Foo *obj, std::string methodname)
{
   std::map<std::string, void (Foo::*)() >::iterator p=
    methods.find(methodname);

  if (p == methods.end())
     throw "You are a bozo";

  (obj->*(p->second))();
}

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