Editing Constructor (object-oriented programming) (section)

=== Raku ===
In [[Raku (programming language)|Raku]], even more boilerplate can be omitted, given that a default ''new'' method is inherited, attributes can be specified, and whether they can be set, reset, or are required. In addition, any extra constructor functionality can be included in a ''BUILD'' method which will get called to allow for custom initialization.  A ''TWEAK'' method can be specified to post-process any attributes already (implicitly) initialized.

<syntaxhighlight lang="perl6">
class Person {
    has Str $.first-name is required; # First name (a string) can only be set at
                                      # construction time (the . means "public").
    has Str $.last-name is required;  # Last name (a string) can only be set at
                                      # construction time (a ! would mean "private").
    has Int $.age is rw;              # Age (an integer) can be modified after 
                                      # construction ('rw'), and is not required
                                      # during the object instantiation.
    
    # Create a 'full-name' method which returns the person's full name.
    # This method can be accessed outside the class.
    method full-name { $!first-name.tc ~ " " ~ $!last-name.tc }

    # Create a 'has-age' method which returns true if age has been set.
    # This method is used only inside the class so it's declared as "private"
    # by prepending its name with a !
    method !has-age { self.age.defined }
  
    # Check custom requirements
    method TWEAK {
        if self!has-age && $!age < 18 { # No under 18
            die "No person under 18";
        }
    }
}
</syntaxhighlight>

The Person class is instantiated like this:
<syntaxhighlight lang="perl6">
my $p0 = Person.new( first-name => 'Sam', last-name => 'Ashe', age => 42 );
my $p1 = Person.new( first-name => 'grace', last-name => 'hopper' );
say $p1.full-name(); # OUTPUT: «Grace Hopper␤»
</syntaxhighlight>

Alternatively, the [[named parameter]]s can be specified using the colon-pair syntax in Perl 6:
<syntaxhighlight lang="perl6">
my $p0 = Person.new( :first-name<Sam>, :last-name<Ashe>, :age(42) );
my $p1 = Person.new( :first-name<Grace>, :last-name<Hopper> );
</syntaxhighlight>

And should you have set up variables with names identical to the named parameters, you can use a shortcut that will use the '''name''' of the variable for the named parameter:
<syntaxhighlight lang="perl6">
my $first-name = "Sam";
my $last-name  = "Ashe";
my $age        = 42;
my $p0 = Person.new( :$first-name, :$last-name, :$age );
</syntaxhighlight>