How do I simulate Delegates in C++?

I created a WatchDog class. For another class to receive messages from WatchDog it must inherit IWatchDog.

class IWatchDog
{
public:
virtual void Timeout( int id ) = 0;
};

The problem is that I need 2 WatchDogs in one class. As you can see I added and id to accomplish this.

Bill

Until now I did not realize that delegates in C# make functional programming possible. Especially constructions as you see nowadays in Ruby and Python and before probably in Smalltalk:

['H','A','L'].collect() {|x| x.succ() }

(this is out of the Ruby book of Thomas Hunt)

Since iterating over collections to transform them is all over the place in most applications this would be a very valuable idiom I think.

I tried to implement something like that in the public review of the generics JSR using some Function class that varies over the argument(s) of the function and over the return type.
Along the lines of
Function<Argument,ReturnType>

But then you'd still have to use the anonymous inner class construction that's so unnecessarily convoluted as Tushar rightly remarks.

Unfortunately it's too late in Java for that to change: I innocently asked Gilad Bracha, the spec lead for generics, for the Ruby construction above to be made possible.

His answer amounted to the effect that he's been lobbying for that for years and that the consensus is that another construction to deal with collections would be too confusing. I got the impression that stance pertained to inner classes too.

By the way: does anybody know wether there's a name for this construction with methods that take a function as an argument?

It's getting tiring to have to always use these long descriptions to refer to this. :-)

Joost

Take a look at this site:

http://www.geocities.com/csharpfaq/

Particularly the delegates section. You might not be so pleased with delagates afterwards :(

> I used to think that delegates were just pure evil until I
> discovered that...
>
>

> void makeUI() {
> ok = new JButton("OK");
> ok.addActionListener(new ActionListener() {
> public void actionPerformed(ActionEvent e) {
> okAction(e);
> }
> });
> }
> 
> void okAction(ActionEvent e) {
> // Handle ActionEvent for the OK button.
> }
> 

>
> ...is just the purity tax that I pay Java. I'd rather say
> less to do the same...
>
>

> void makeUI() {
> ok = new JButton("OK");
> ok.actionEventHandler += new
> += new ActionEventHandler(okAction);
> }
> 
> void okAction(ActionEvent e) {
> // Handle ActionEvent for the OK button.
> }
> 

>
> I'd rather just forget about Anonymous Inner Classes like
> a bad dream. They were really ugly and awkward when I
> first used them. They're still ugly and awkward - I'm just
> used to them now. It's about time a language got used to
> me instead :-)