1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
# Copyright (C) 2007-2012, Parrot Foundation.
=pod
=head1 DESCRIPTION
A tutorial lesson about Parrot's classes.
=head1 CLASSES
If we combine the ideas of namespaces, subroutines, and global variables,
we are well along our way to the concept of a class. Classes are
high-level constructs that keep data and code together into a single
unit.
A class definition in PIR consists of two parts: Creating a new class
PMC object, and creating the methods for that class. The class PMC
can be created with the C<newclass> and C<subclass> opcodes. Data fields,
called "attributes" can be added to the class with the C<addattribute>
opcode. Once a class PMC has been created, objects of that class
can be instantiated like normal with the c<new> opcode.
The functions of a class are called methods, and are created in a
namespace with the same name as the class. In the example below, the
class is called "Foo", and all the methods of that class are located
in C<.namespace ["Foo"]>. Methods also need to have the C<:method>
flag on them, to differentiate them from normal subroutines.
Inside a method, the C<self> keyword acts like an additional parameter
that contains the PMC object of the class that the method was called
on.
This example creates a class "Foo" with two attributes "bar" and "baz".
It also has two setter and two accessor methods, one for each attribute.
=cut
.sub main :main
.local pmc myclass, myobj
myclass = newclass 'Foo'
addattribute myclass, 'bar'
addattribute myclass, 'baz'
myobj = new ['Foo']
myobj.'set_bar'("Hello")
myobj.'set_baz'(5)
$S0 = myobj.'get_bar'()
say $S0
$I0 = myobj.'get_baz'()
print $I0
print "\n"
.end
.namespace ['Foo']
.sub get_bar :method
$P0 = getattribute self, "bar"
.return($P0)
.end
.sub set_bar :method
.param string value
$P0 = new ['String']
$P0 = value
setattribute self, "bar", $P0
.end
.sub get_baz :method
$P0 = getattribute self, "baz"
.return($P0)
.end
.sub set_baz :method
.param int value
$P0 = new ['Integer']
$P0 = value
setattribute self, "baz", $P0
.end
# Local Variables:
# mode: pir
# fill-column: 100
# End:
# vim: expandtab shiftwidth=4 ft=pir:
|
