Re: [Vala] anonymous functions

[Jürg Billeter <j bitron ch>]

On Tue, 2008-07-15 at 11:11 +0100, Sam Liddicott wrote:
> * Ali Sabil wrote, On 15/07/08 10:47: 
> > Signal handler always have the "signal sender" as 1st parameter, in
> > this case it would be the AdvancedSample instance from which the
> > "foo" signal originated.
> >
> > I proposed the "sender" keyword inside signal handler context (just
> > like the "this" keyword inside the object instance context) to
> > eliminate this confusing parameter a while ago, but it didn't seem
> > like a good idea for many people.
> Hmmm... this makes me feel uncomfortable in the same way the glade
> example callbacks make me feel uncomfortable, there seem to be
> implicit parameters which are not defined in the prototypes, you just
> have to "know", the s was not referenced in the foo signal declaration
> either. 

The issue is that the sender parameter, that all signal handlers have,
is not a signal parameter, it's really just a signal handler parameter.
When emitting the signal (and soon also in virtual signal methods),
there is no sender parameter as `this` is the same as the sender.

I don't quite understand what exactly makes you feel uncomfortable, the
fact that you don't have to specify the sender when declaring the
signal, the proposed sender keyword, or something else?

> Is this anonymous signal handler invoked as a flat function or method?
> Does "this" have a value (I guess it does or the use of name would
> fail) in which case, surely s must be declared somewhere else...

It's invoked as an instance method. The example is a bit special in that
the same instance emits and handles the signal. In general `this` and
the sender are two separate objects. `s.name`, `this.name`, and `name`

Juerg