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<TITLE>28.1.9.2. Declaring the Validity of Initialization Arguments</TITLE>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html5335 HREF="node295.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html5333 HREF="node292.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html5327 HREF="node293.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html5337 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html5338 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html5336 HREF="node295.html"> Defaulting of Initialization </A>
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<B>Up:</B> <A NAME=tex2html5334 HREF="node292.html"> Object Creation and </A>
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<B> Previous:</B> <A NAME=tex2html5328 HREF="node293.html"> Initialization Arguments</A>
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<HR> <P>
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<H3><A NAME=SECTION003219200000000000000>28.1.9.2. Declaring the Validity of Initialization Arguments</A></H3>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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<A NAME=DeclaringtheValidityofInitializationArgumentsSECTION>Initialization</A>
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arguments are checked for validity in each of the four
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situations that use them. An initialization argument may be valid in
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one situation and not another. For example, the system-supplied
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primary method for <tt>make-instance</tt> defined for the class
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<tt>standard-class</tt> checks the validity of its initialization arguments
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and signals an error if an initialization argument is supplied that is
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not declared valid in that situation.
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<P>
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There are two means of declaring initialization arguments valid.
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<P>
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<UL><LI> Initialization arguments that fill slots are declared
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valid by the <tt>:initarg</tt> slot option to <tt>defclass</tt>. The
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<tt>:initarg</tt> slot option is inherited from superclasses. Thus the set of
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valid initialization arguments that fill slots for a class is the
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union of the initialization arguments that fill slots declared
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valid by that class and its superclasses. Initialization arguments
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that fill slots are valid in all four contexts.
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<P>
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<LI> Initialization arguments that supply arguments to methods
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are declared valid by defining those methods. The keyword name of
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each keyword parameter specified in the method's lambda-list becomes
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an initialization argument for all classes for which the method is
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applicable. Thus method inheritance controls the set of valid
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initialization arguments that supply arguments to methods. The
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generic functions for which method definitions serve to declare
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initialization arguments valid are as follows:
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<P>
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<UL><LI> Making an instance of a class: <tt>allocate-instance</tt>,
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<tt>initialize-instance</tt>, and <tt>shared-initialize</tt>.
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Initialization arguments declared valid by these methods are
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valid when making an instance of a class.
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<P>
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<LI> Re-initializing an instance: the functions <tt>reinitialize-instance</tt>
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and <tt>shared-initialize</tt>.
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Initialization arguments declared valid by these methods are
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valid when re-initializing an instance.
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<P>
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<LI> Updating an instance to conform to a redefined class:
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<tt>update-instance-for-redefined-class</tt>
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and <tt>shared-initialize</tt>.
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Initialization arguments declared valid by these methods are
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valid when updating an instance to conform to a redefined class.
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<P>
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<LI> Updating an instance to conform to the definition of a
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different class: <tt>update-instance-for-different-class</tt> and
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<tt>shared-initialize</tt>.
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Initialization arguments declared valid by these methods are
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valid when updating an instance to conform to the definition
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of a different class.
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</UL>
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</UL>
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<P>
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The set of valid initialization arguments for a class is the set of
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valid initialization arguments that either fill slots or supply
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arguments to methods, along with the predefined initialization
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argument <tt>:allow-other-keys</tt>. The default value for
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<tt>:allow-other-keys</tt> is <tt>nil</tt>. The meaning of
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<tt>:allow-other-keys</tt> is the same here as when it is passed to an ordinary
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function.
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<P>
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<BR> <HR><A NAME=tex2html5335 HREF="node295.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html5333 HREF="node292.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html5327 HREF="node293.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html5337 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html5338 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html5336 HREF="node295.html"> Defaulting of Initialization </A>
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<B>Up:</B> <A NAME=tex2html5334 HREF="node292.html"> Object Creation and </A>
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<B> Previous:</B> <A NAME=tex2html5328 HREF="node293.html"> Initialization Arguments</A>
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<HR> <P>
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