class question

27 Nov 2007 10:00 AM

Gunawan

hi all,
I have an issue. It's rather hard to explain. I hope you all could
understand.

I would like to create a class let's say myclass.
in myclass I have some static void function

myclass.function1()
myclass.function2() and so on.

If I need to use function1() I could just type
myclass.function1();

and it works.

I would like to know is there any function that I can use to call a static
function.
so I can call function1 like this
whatfunction("myclass.function1()");

whatfunction("myclass.function2()");

Hopefully you can help me with this.

Regards,
Gun

27 Nov 2007 10:16 AM

Marc Gravell

Depending on the scenario, there are two options... if you know the
names at compile time, but need a way of takling about the method in
an abstract way (interchangeable with a range of such functions) then
a delegate is the answer...

MethodInvoker myMethod = myclass.function1; // note no brackets

then later...

myMethod();

---

The alternative is reflection -
typeof(myclass).GetMethod("function1").Invoke(null, null)

Note that reflaction is generally considered the less preferable
option, and gives you no compile-time checking.

Marc

28 Nov 2007 11:57 AM

Rick Lones

Gunawan wrote:

> I would like to create a class let's say myclass.
> in myclass I have some static void function
>
> myclass.function1()
> myclass.function2() and so on.
>
> I would like to know is there any function that I can use to call a static
> function.
> so I can call function1 like this
> whatfunction("myclass.function1()");
>
> whatfunction("myclass.function2()");

Some might say this is a bit perverted . . . but just for fun:

using System;
using System.Collections;

namespace WeirdFunctionCall
{
   class MyClass
   {
     delegate void myFunc();
     static Hashtable whatfunction = new Hashtable();

     [STAThread]
     static void Main(string[] args)
     {
       whatfunction.Add("myclass.function1()", new myFunc(MyClass.f1));
       whatfunction.Add("myclass.function2()", new myFunc(MyClass.f2));
       whatfunction.Add(" . . . and so on", new myFunc(MyClass.f3));

       ((myFunc)whatfunction["myclass.function1()"])();
       ((myFunc)whatfunction["myclass.function2()"])();
       ((myFunc)whatfunction[" . . . and so on"])();

       Console.ReadLine();
     }

     static void f1() {Console.WriteLine("f1 here . . .");}
     static void f2() {Console.WriteLine("f2 here . . .");}
     static void f3() {Console.WriteLine("f3 here . . .");}

   }
}

I have actually done things kind of like this, don't remember why it seemed like
a good idea at the time. I suppose that in VS2005 you could use a generic
Hashtable<string, myFunc> and avoid the explicit cast when invoking.

HTH,
-rick-

29 Nov 2007 7:27 AM

Gunawan

Show quote

"Rick Lones" <Wrlon***@YcharterZ.net> wrote in message
news:PIc3j.5$wN5.0@newsfe05.lga...
> Gunawan wrote:
>
>> I would like to create a class let's say myclass.
>> in myclass I have some static void function
>>
>> myclass.function1()
>> myclass.function2() and so on.
>>
>> I would like to know is there any function that I can use to call a
>> static function.
>> so I can call function1 like this
>> whatfunction("myclass.function1()");
>>
>> whatfunction("myclass.function2()");
>
> Some might say this is a bit perverted . . . but just for fun:
>
> using System;
> using System.Collections;
>
> namespace WeirdFunctionCall
> {
>   class MyClass
>   {
>     delegate void myFunc();
>     static Hashtable whatfunction = new Hashtable();
>
>     [STAThread]
>     static void Main(string[] args)
>     {
>       whatfunction.Add("myclass.function1()", new myFunc(MyClass.f1));
>       whatfunction.Add("myclass.function2()", new myFunc(MyClass.f2));
>       whatfunction.Add(" . . . and so on", new myFunc(MyClass.f3));
>
>       ((myFunc)whatfunction["myclass.function1()"])();
>       ((myFunc)whatfunction["myclass.function2()"])();
>       ((myFunc)whatfunction[" . . . and so on"])();
>
>       Console.ReadLine();
>     }
>
>     static void f1() {Console.WriteLine("f1 here . . .");}
>     static void f2() {Console.WriteLine("f2 here . . .");}
>     static void f3() {Console.WriteLine("f3 here . . .");}
>
>   }
> }
>
> I have actually done things kind of like this, don't remember why it
> seemed like a good idea at the time. I suppose that in VS2005 you could
> use a generic Hashtable<string, myFunc> and avoid the explicit cast when
> invoking.
>
> HTH,
> -rick-

Thank you rick, though I'm not quite understand...
Is there any other solution?

Regards,
Gun

29 Nov 2007 12:29 PM

Rick Lones

Gunawan wrote:
Show quote

> "Rick Lones" <Wrlon***@YcharterZ.net> wrote in message
> news:PIc3j.5$wN5.0@newsfe05.lga...
>> Gunawan wrote:
>>
>>> I would like to create a class let's say myclass.
>>> in myclass I have some static void function
>>>
>>> myclass.function1()
>>> myclass.function2() and so on.
>>>
>>> I would like to know is there any function that I can use to call a
>>> static function.
>>> so I can call function1 like this
>>> whatfunction("myclass.function1()");
>>>
>>> whatfunction("myclass.function2()");
>> Some might say this is a bit perverted . . . but just for fun:
>>
>> using System;
>> using System.Collections;
>>
>> namespace WeirdFunctionCall
>> {
>>   class MyClass
>>   {
>>     delegate void myFunc();
>>     static Hashtable whatfunction = new Hashtable();
>>
>>     [STAThread]
>>     static void Main(string[] args)
>>     {
>>       whatfunction.Add("myclass.function1()", new myFunc(MyClass.f1));
>>       whatfunction.Add("myclass.function2()", new myFunc(MyClass.f2));
>>       whatfunction.Add(" . . . and so on", new myFunc(MyClass.f3));
>>
>>       ((myFunc)whatfunction["myclass.function1()"])();
>>       ((myFunc)whatfunction["myclass.function2()"])();
>>       ((myFunc)whatfunction[" . . . and so on"])();
>>
>>       Console.ReadLine();
>>     }
>>
>>     static void f1() {Console.WriteLine("f1 here . . .");}
>>     static void f2() {Console.WriteLine("f2 here . . .");}
>>     static void f3() {Console.WriteLine("f3 here . . .");}
>>
>>   }
>> }
>>
>> I have actually done things kind of like this, don't remember why it
>> seemed like a good idea at the time. I suppose that in VS2005 you could
>> use a generic Hashtable<string, myFunc> and avoid the explicit cast when
>> invoking.
>>
>> HTH,
>> -rick-
>
>
> Thank you rick, though I'm not quite understand...
> Is there any other solution?
>

As Marc said, it depends on your actual problem. It appears from your original
question that you are being handed a string which names a function which is
"known" to you at compile time and you are just looking for a convenient way to
get from the string to the function it identifies. In this case there are a lot
of ways, ranging from some kind of delegate mechanism to something as simple as
a switch statement. (E.g., case "function1": myClass.function1(); break;) My
example above is a somewhat tongue-in-cheek example of using delegates, but it
does work just fine. It uses a Hashtable to map name strings to delegates.

That said, I have to wonder why you would want your functions to be invoked in
this rather indirect way at all. Is there some reason they can't just be
exposed directly as public static methods of of your class?

-rick-