shadow

NAME

shadow() - shadow one or more functions in some object

SYNOPSIS

object shadow( object ob, int flag );

DESCRIPTION

If  'flag'  is  1  or missing, then current object will shadow 'ob'. If
'flag' is 0, then either 0 will be returned,  or  the  object  that  is
already shadowing 'ob'.

The master object defines the function "valid_shadow()".  If it returns
1 the target object can't be shadowed, and the "shadow()" function will
return 0 instead of 'ob'.

If  an object 'a' shadows an object 'b', then all "call_other(func)" to
'b' will be redirected to 'a'. If object 'a' has not defined the  func‐
tion,  then  the  call  will  be  forwarded to 'b' (as if there were no
shadow).  There is only one object that can call functions in 'b'  with
call_other(),  and  that is 'a'. Not even object 'b' can "call_other()"
itself. All normal (internal) function calls inside  'b'  will  however
remain internal to 'b'.

There  are  two  ways  to remove the shadow. Either destruct it, or the
object that was shadowed. In the latter case, the shadow will  also  be
destructed automatically.

The result is that it is possible to hide an object behind another one,
but everything can be  totally  transparent.   The  shadow()  efunction
makes  it possible to change the behavior of an object without changing
the code for the object in question.  One possible use for shadow()  is
to  add  special  capabilities  to  various  classes of players (thief,
fighter, mage, etc).  This usage would make it  possible  to  keep  the
player object much simpler than it could be if the code for the various
classes had to be in the player object itself.

SEE ALSO

destruct(3), shadowp(3), query_shadowing(3), valid_shadow(4)