Delegate

  • Thread starter Thread starter Joanne
  • Start date Start date
J

Joanne

A delegate is said to be good for the programmer since it
provides a good way of invoking methods which are not
exactly known until run time.

What does "good" mean here?

If i declare myDelegate and associate some method with
it, am I not knowing which method will be executed?

Is the following code correct? I have the idea that the
delegate is not being properly associated with the event,
although the targeted method is invoked just fine.

//class members
delegate void handlerDelegate();
event handlerDelegate ON_a;

//note: outputText matches the delegate signature
this.ON_a += new MyClass.handlerDelegate
this.outputText);
//call the event
ON_a();
 
hi joanne,

your delegate an call seems (to me) to be correct. (just i don't know if you
can have a delegate inside a class, may be you can)
just verify if the event is full befor call the event
if(ON_a!=null) ON_a();

seems i do not help :p
ROM
 
A delegate is said to be good for the programmer since it
provides a good way of invoking methods which are not
exactly known until run time.

What does "good" mean here?
Click to expand...

it surely means "safe".

think of delegates as of "type-safe function pointers". even the declaration
is similar:

typedef int (*pf)(int); // C-style function pointer
delegate int pf(int n); // C#-style delegate

the difference is clearly visible while you create an instance of the
function pointer:

// C-style cast will always succeed...
pf f = (pf)GetProcAddress(...);
// ...so the call can cause severe problems if wrong signature is used
int a = f(5);

// C#-style delegate creation will raise an exception if the signatures are
different...
pf f = new pf( ... );
// ...so the call is always safe
int a = f(5);

regards,
Wiktor
 
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