class ValueObjAt

Unique identification for value types

class ValueObjAt is ObjAt { }

A subclass of ObjAt that should be used to indicate that a class produces objects that are value types - in other words, that are immutable after they have been initialized.

my %h = a => 42;        # mutable Hash 
say %h.WHICH;           # OUTPUT: «ObjAt.new("Hash|1402...888")␤» 
 
my %m is Map = a => 42; # immutable Map 
say %m.WHICH;           # OUTPUT: «ValueObjAt.new("Map|AAF...09F61F")␤»

If you create a class that should be considered a value type, you should add a WHICH method to that class that returns a ValueObjAt object, for instance:

class YourClass {
    has $.foo;  # note these are not mutable 
    has $.bar;
 
    method WHICH() {
        ValueObjAt.new("YourClass|$!foo|$!bar");
    }
}

Note that it is customary to always start the identifying string with the name of the object, followed by a "|". This to prevent confusion with other classes that may generate similar string values: the name of the class should then be enough of a differentiator to prevent collisions.