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
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
|
<ppdoc>
<copyright>
Copyright (c) 2001 by Addison Wesley Longman. This
material may be distributed only subject to the terms and
conditions set forth in the Open Publication License, v1.0 or
later (the latest version is presently available at
http://www.opencontent.org/openpub/).
</copyright>
<class name="Class" super="Module" type="class">
<p/>
Classes in Ruby are first-class objects---each is an instance of
class <classname>Class</classname>.
<p/>
When a new class is created (typically using
<tt>class<nbsp/>Name<nbsp/>...<nbsp/>end</tt>), an object of type <classname>Class</classname> is created
and assigned to a global constant (<tt>Name</tt> in this case). When
<tt>Name.new</tt> is called to create a new object, the <meth>new</meth>
method in <classname>Class</classname> is run by default. This can be demonstrated by
overriding <meth>new</meth> in <classname>Class</classname>:
<p/>
<codefragment>
<alltt><fullcode><![CDATA[ class Class
alias oldNew new
def new(*args)
print "Creating a new ", self.name, "\n"
oldNew(*args)
end
end
class Name
end
n = Name.new
]]></fullcode>
class<nbsp/>Class
<nbsp/><nbsp/><nbsp/>alias<nbsp/>oldNew<nbsp/><nbsp/>new
<nbsp/><nbsp/><nbsp/>def<nbsp/>new(*args)
<nbsp/><nbsp/><nbsp/><nbsp/><nbsp/>print<nbsp/>"Creating<nbsp/>a<nbsp/>new<nbsp/>",<nbsp/>self.name,<nbsp/>"\n"
<nbsp/><nbsp/><nbsp/><nbsp/><nbsp/>oldNew(*args)
<nbsp/><nbsp/><nbsp/>end
<nbsp/>end
<p/>
<nbsp/>class<nbsp/>Name
<nbsp/>end
<p/>
<nbsp/>n<nbsp/>=<nbsp/>Name.new
</alltt>
</codefragment>
<em>produces:</em>
<codefragment><alltt>
Creating<nbsp/>a<nbsp/>new<nbsp/>Name
</alltt>
</codefragment>
<p/>
<methods type="class">
<method name="inherited" ref="inherited">
<callseq>
<obj>aClass</obj>.inherited( <obj>aSubClass</obj> )
</callseq>
<desc>
<p/>
This is a singleton method (per class) invoked by Ruby when a subclass
of <obj>aClass</obj> is created. The new subclass is passed as a
parameter.
<p/>
<codefragment>
<alltt><fullcode><![CDATA[ class Top
def Top.inherited(sub)
print "New subclass: ", sub, "\n"
end
end
class Middle < Top
end
class Bottom < Middle
end
]]></fullcode>
class<nbsp/>Top
<nbsp/><nbsp/>def<nbsp/>Top.inherited(sub)
<nbsp/><nbsp/><nbsp/><nbsp/>print<nbsp/>"New<nbsp/>subclass:<nbsp/>",<nbsp/>sub,<nbsp/>"\n"
<nbsp/><nbsp/>end
end
<p/>
class<nbsp/>Middle<nbsp/><<nbsp/>Top
end
<p/>
class<nbsp/>Bottom<nbsp/><<nbsp/>Middle
end
</alltt>
</codefragment>
<em>produces:</em>
<codefragment><alltt>
New<nbsp/>subclass:<nbsp/>Middle
New<nbsp/>subclass:<nbsp/>Bottom
</alltt>
</codefragment>
<p/>
</desc>
</method>
<p/>
<method name="new" ref="new">
<callseq>
Class.new( <obj>aSuperClass</obj>=<classname>Object</classname> )
<returns><obj>aClass</obj></returns>
</callseq>
<desc>
<p/>
Creates a new anonymous (unnamed)
class with the given superclass (or
<classname>Object</classname> if no parameter is given).
<p/>
</desc>
</method>
<p/>
</methods>
<p/>
<methods type="instance">
<p/>
<method name="new" ref="new">
<callseq>
<obj>aClass</obj>.new( <optz><obj>args</obj></optz> )
<returns><obj>anObject</obj></returns>
</callseq>
<desc>
<p/>
Creates a new object of <obj>aClass</obj>'s class, then invokes that object's
<meth>initialize</meth> method, passing it <obj>args</obj>.
<p/>
</desc>
</method>
<p/>
<method name="superclass" ref="superclass">
<callseq>
<obj>aClass</obj>.superclass
<returns><obj>aSuperClass</obj> or <tt>nil</tt></returns>
</callseq>
<desc>
<p/>
Returns the superclass of <obj>aClass</obj>, or <const>nil</const>.
<p/>
<codefragment>
<fullcode><![CDATA[ Class.superclass
Object.superclass
]]></fullcode><rubycode>
<tr>
<td><tt>Class.superclass</tt></td>
<td>»</td>
<td><tt>Module</tt></td>
</tr>
<tr>
<td><tt>Object.superclass</tt></td>
<td>»</td>
<td><tt>nil</tt></td>
</tr>
</rubycode>
<p/>
</codefragment>
<p/>
</desc>
</method>
<p/>
</methods>
<p/>
</class>
</ppdoc>
|
