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
|
'\"
'\" Copyright (c) 2018 Donal K. Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH abstract n 0.3 TclOO "TclOO Commands"
.so man.macros
.BS
'\" Note: do not modify the .SH NAME line immediately below!
.SH NAME
oo::abstract \- a class that does not allow direct instances of itself
.SH SYNOPSIS
.nf
package require tcl::oo
\fBoo::abstract\fI method \fR?\fIarg ...\fR?
.fi
.SH "CLASS HIERARCHY"
.nf
\fBoo::object\fR
\(-> \fBoo::class\fR
\(-> \fBoo::abstract\fR
.fi
.BE
.SH DESCRIPTION
Abstract classes are classes that can contain definitions, but which cannot be
directly manufactured; they are intended to only ever be inherited from and
instantiated indirectly. The characteristic methods of \fBoo::class\fR
(\fBcreate\fR and \fBnew\fR) are not exported by an instance of
\fBoo::abstract\fR.
.PP
Note that \fBoo::abstract\fR is not itself an instance of \fBoo::abstract\fR.
.SS CONSTRUCTOR
The \fBoo::abstract\fR class does not define an explicit constructor; this
means that it is effectively the same as the constructor of the
\fBoo::class\fR class.
.SS DESTRUCTOR
The \fBoo::abstract\fR class does not define an explicit destructor;
destroying an instance of it is just like destroying an ordinary class (and
will destroy all its subclasses).
.SS "EXPORTED METHODS"
The \fBoo::abstract\fR class defines no new exported methods.
.SS "NON-EXPORTED METHODS"
The \fBoo::abstract\fR class explicitly states that \fBcreate\fR,
\fBcreateWithNamespace\fR, and \fBnew\fR are unexported.
.SH EXAMPLES
.PP
This example defines a simple class hierarchy and creates a new instance of
it. It then invokes a method of the object before destroying the hierarchy and
showing that the destruction is transitive.
.PP
.CS
\fBoo::abstract\fR create fruit {
method eat {} {
puts "yummy!"
}
}
oo::class create banana {
superclass fruit
method peel {} {
puts "skin now off"
}
}
set b [banana \fBnew\fR]
$b peel \fI\(-> prints 'skin now off'\fR
$b eat \fI\(-> prints 'yummy!'\fR
set f [fruit new] \fI\(-> error 'unknown method "new"...'\fR
.CE
.SH "SEE ALSO"
oo::define(n), oo::object(n)
.SH KEYWORDS
abstract class, class, metaclass, object
.\" Local variables:
.\" mode: nroff
.\" fill-column: 78
.\" End:
|
