Question

Im having the following in my Swig interface file interfacing a .c/.h for a small GUI library:

%{
    void Widget_name_set( Widget *widget, char *name )
    {
        if( !name ) return;

        WidgetSetName( widget, name );
    }


    char *Widget_name_get( Widget *widget )
    {
        return WidgetGetName( widget );
    }
%}


struct Widget
{
    %extend
    {           
        char name[ 32 ];

        Widget( void )
        {
            return WidgetNew();
        }


        ~Widget()
        {
            if( $self ) WidgetDelete( $self );
        }


        void SetName( char *name )
        {
            Widget_name_set( $self, name );
        }


        char *GetName()
        {
            return Widget_name_get( $self );
        }
    }
};

Then I use the interface file to generate a Lua wrapper. The results are almost as expected if I call in Lua the following:

w = Widget(); 
w:SetName("test");

Everything is ok. But if I do this:

w = Widget(); 
w.SetName( nil, "test" );

It obviously crash as the parameter is nil. Is there a way (either using the Swig interface or in Lua) to suppress all the call with a dot and only keep the one with column? Like this it would be easier for the user and will avoid me to add 10 million checks of pointers etc…

Answer 1

Is there a way (either using the Swig interface or in Lua) to suppress all the call with a dot and only keep the one with column?

No. It’s just semantic sugar as far as Lua is concerned. Using . means to just access the member. Using : means that when you call the function, the first parameter is the table being accessed with :.

You probably couldn’t even tell the difference from inspecting the Lua disassembly (though admittedly, that’s just guessing on my part); by then, it’s probably been converted into its final form.