Re: C++-classes.

[James Durie <jdurie anvil co uk>]

On Fri, 2002-10-18 at 09:23, David Larsson wrote:
> Hi.
>
> How do you get this to work.
>
> /* Class Definition */
> class GtkClass
> {
>   public:
>     void GtkClass();
>     void Test();
>   private:
>     GtkWidget *button;
> };
>
> GtkClass::GtkClass()
> {
>   button=gtk_button_new();
>
>   /* The part that doesn't work. */
>   gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(Test), NULL);
> }
>
> How is the Method Test to be declared, and how do you call it from a gtk_signal_connect()?
>
> Thanks
>
> // David

You can't pass a method in as a callback function pointer. There is a
hidden parameter, this, to all methods which points to the instance of
the class.

Instead try:
gtk_signal_connect(GTK_OBJECT(button), "clicked",
GTK_SIGNAL_FUNC(clicked_cb), this);


where clicked_cb is:
void clicked_cb(GtkButton *button, GtkClass *c)
{
        c->Test();
}


That is the simplest way to get a callback calling a method and how I
have done it in my own projects.

James


-- 
James Durie               Phone:  +44 20 7749 7904
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