ItemNotPresent class - Revision history

JAL: link repair

2014-11-18T21:31:16Z

link repair

← Older revision		Revision as of 21:31, 18 November 2014
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	The methods in the class are described in the subsections that follow. In addition:		The methods in the class are described in the subsections that follow. In addition:
	<ul>		<ul>
	<li>[[Notation conventions for methods~~\|"Notation conventions for methods"~~]] has information		<li>[[Notation conventions for methods]] has information about the conventions followed. </li>
	about the conventions followed.		<li>[[ItemNotPresent methods syntax]] is a single page that contains the syntax diagrams of all the methods in the class. </li>
	<li>[[ItemNotPresent methods syntax~~\|"ItemNotPresent methods syntax"~~]] is a single page that contains the syntax diagrams of all the methods in the class.
	</ul>		</ul>

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	<tr><th><var>[%(ItemNotPresent):]</var></th>		<tr><th><var>[%(ItemNotPresent):]</var></th>
	<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors\|Constructor]]</var>. See [[#Usage notes\|"Usage notes"]], below, for more information about invoking an <var>ItemNotPresent</var><var>Constructor</var>.</td></tr>		<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors\|Constructor]]</var>. See [[#Usage notes\|Usage notes]], below, for more information about invoking an <var>ItemNotPresent</var><var>Constructor</var>.</td></tr>
	</table>		</table>

	===Usage notes===		===Usage notes===
	<ul>		<ul>
	<li>As described in [[Object variables#Using New or other Constructors\|"Using New or other Constructors"]],<var>New</var> can be invoked with no object, with an explicit class name, or with an object variable in the class, even if that object is <var>Null</var>:<p class="code">%itemnp = new		<li>As described in [[Object variables#Using New or other Constructors\|Using New or other Constructors]],<var>New</var> can be invoked with no object, with an explicit class name, or with an object variable in the class, even if that object is <var>Null</var>:<p class="code">%itemnp = new

	%itemnp = %(ItemNotPresent):new		%itemnp = %(ItemNotPresent):new

JAL at 22:28, 26 November 2012

2012-11-26T22:28:25Z

New page

__NOTOC__
An <var>ItemNotPresent</var> exception indicates that an explict or implicit <var>NamedArraylist</var> <var>[[Item (NamedArraylist property)|Item]]</var> method requested a value not present on the <var>NamedArrayList</var>. <var>NamedArraylist</var> here can mean the [[NamedArraylist class]], [[FloatNamedArraylist class]], or [[UnicodeNamedArraylist class]].

This exception class has no properties. It is simply a notification that requested item was not present on the <var>NamedArrayList</var>.

The class's only method is the <var>[[New_(ItemNotPresent_constructor)|New]]</var> constructor, which you would typically use with a <var class="product">User Language</var> <var>[[Throw statement|Throw]]</var> statement to produce an <var>ItemNotPresent</var> exception yourself.
For example:
<p class="code">throw %(itemNotPresent):new
</p>

Remember that you catch an exception with the <var>[[Exceptions#Try and Catch|Catch]]</var> statement; if an exception condition occurs outside a
<var>Catch</var> for it, the request is cancelled.
For example, if you think it is possible that a value is not on the <var>NamedArraylist</var>, you can do:
<p class="code">[[Exceptions#Try and Catch|try]] %value = %valueList(%string)
... process the value
[[Exceptions#Try and Catch|catch]] itemNotPresent
end try
</p>

On the other hand, if you always expect the item to be present, you might want a program crash to result if you are wrong about the match, so you could leave out a <var>Try/Catch</var>.

The <var>Try/Catch</var> approach is slightly more efficient than testing for a zero result with the [[Number (NamedArraylist function)]] function, [[Number (FloatNamedArraylist function)]], or [[Number (UnicodeNamedArraylist function)]]). <var>Try</var> generates no quads other than the branch around the <var>Catch</var> block if the item is present. If <var>UseDefault</var> is set to <code>True</code> for the <var>NamedArraylist</var>, an <var>ItemNotPresent</var> exception is never thrown. Using a default value for not-present items is more efficient but less flexible than catching an <var>ItemNotPresent</var> exception.

The <var>ItemNotPresent</var> class is available as of <var class="product">Sirius Mods</var> version 8.0.

The most common use of the <var>ItemNotPresent</var> exception class is in <var>NamedArraylists</var> that are used as a cache for expensive-to-produce values or objects. For example, if <code>%recordsets</code> is a <var>NamedArraylist</var> of [[Recordset class|Recordset objects]] (in some file), the following is an example of how one might avoid doing a <var>Find</var> more than once for a specific value:
<p class="code">for %i from 1 to %keys:count
%key = %key(%i)
try %recordset = %recordsets(%key)
catch itemNotPresent
find records to %recordset
key = %key
end find
%recordsets(%key) = %recordset
end try
end for
</p>

==The ItemNotPresent methods==
<div class="showVisit">
<table class="wikitable">
<tr><th>Method</th><th>Description</th></tr>
<tr><td valign="top">[[New (ItemNotPresent constructor)|New]]</td><td valign="top">Create a new ItemNotPresent object</td></tr>
</table>
</div>

The methods in the class are described in the subsections that follow. In addition:
<ul>
<li>[[Notation conventions for methods|"Notation conventions for methods"]] has information
about the conventions followed.
<li>[[ItemNotPresent methods syntax|"ItemNotPresent methods syntax"]] is a single page that contains the syntax diagrams of all the methods in the class.
</ul>

==New constructor==
{{Template:ItemNotPresent:New subtitle}}

This method generates an instance of an <var>[[ItemNotPresent_class|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:

===Syntax===
{{Template:ItemNotPresent:New syntax}}
====Syntax terms====
<table class="syntaxTable">

<tr><th>%itemNotPresent</th>
<td>An <var>ItemNotPresent</var> %variable which will refer to the newly created object.
</td></tr>

<tr><th><var>[%(ItemNotPresent):]</var></th>
<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors|Constructor]]</var>. See [[#Usage notes|"Usage notes"]], below, for more information about invoking an <var>ItemNotPresent</var><var>Constructor</var>.</td></tr>
</table>

===Usage notes===
<ul>
<li>As described in [[Object variables#Using New or other Constructors|"Using New or other Constructors"]],<var>New</var> can be invoked with no object, with an explicit class name, or with an object variable in the class, even if that object is <var>Null</var>:<p class="code">%itemnp = new

%itemnp = %(ItemNotPresent):new

%itemnp = %itemnp:new
</p>
</ul>

[[Category:System exception classes]]

JAL2 at 18:04, 7 August 2012

2012-08-07T18:04:31Z

← Older revision		Revision as of 18:04, 7 August 2012
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	~~<h2>~~New constructor~~</h2>~~		==New constructor==
	{{Template:ItemNotPresent:New subtitle}}		{{Template:ItemNotPresent:New subtitle}}

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	<h4>Syntax terms</h4>		<h4>Syntax terms</h4>
	<table class="syntaxTable">		<table class="syntaxTable">

	<tr><th>%itemNotPresent</th>		<tr><th>%itemNotPresent</th>
	<td>An <var>ItemNotPresent</var> %variable which will refer to the newly created object.		<td>An <var>ItemNotPresent</var> %variable which will refer to the newly created object.
	</td></tr>		</td></tr>
	<tr><th><var>%(ItemNotPresent)</var></th>
			<tr><th><var>[%(ItemNotPresent):]</var></th>
	<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors\|Constructor]]</var>. See [[#Usage notes\|"Usage notes"]], below, for more information about invoking an <var>ItemNotPresent</var><var>Constructor</var>.</td></tr>		<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors\|Constructor]]</var>. See [[#Usage notes\|"Usage notes"]], below, for more information about invoking an <var>ItemNotPresent</var><var>Constructor</var>.</td></tr>
	</table>		</table>

JAL2 at 21:51, 31 July 2012

2012-07-31T21:51:13Z

← Older revision		Revision as of 21:51, 31 July 2012
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	<var>Catch</var> for it, the request is cancelled.		<var>Catch</var> for it, the request is cancelled.
	For example, if you it's possible a value is not on the NamedArraylist you can do:		For example, if you it's possible a value is not on the NamedArraylist you can do:
	<p class="code">[[try]] %value = %valueList(%string)		<p class="code">[[Exceptions#Try and Catch\|try]] %value = %valueList(%string)
	... process the value		... process the value
	[[catch]] itemNotPresent		[[Exceptions#Try and Catch\|catch]] itemNotPresent
	end try		end try
	</p>		</p>

JAL2 at 22:19, 30 March 2012

2012-03-30T22:19:18Z

← Older revision		Revision as of 22:19, 30 March 2012
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	{{Template:ItemNotPresent:New subtitle}}		{{Template:ItemNotPresent:New subtitle}}

	This ~~constructor~~ generates an instance of an <var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:		This method generates an instance of an <var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:

	<h3>Syntax</h3>		<h3>Syntax</h3>

JAL2 at 22:17, 30 March 2012

2012-03-30T22:17:34Z

← Older revision		Revision as of 22:17, 30 March 2012
Line 57:		Line 57:
	{{Template:ItemNotPresent:New subtitle}}		{{Template:ItemNotPresent:New subtitle}}

	This ~~[[Notation conventions for methods\|callable]]~~ constructor generates an instance of an <var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:		This constructor generates an instance of an <var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:

	<h3>Syntax</h3>		<h3>Syntax</h3>

Alex at 21:10, 19 October 2011

2011-10-19T21:10:04Z

← Older revision		Revision as of 21:10, 19 October 2011
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	<h2>The ItemNotPresent methods</h2>		<h2>The ItemNotPresent methods</h2>
	~~{{Template:Method list header\|class=ItemNotPresent}}~~
	<div class="showVisit">		<div class="showVisit">
	<table class="wikitable">		<table class="wikitable">

Alex at 21:04, 19 October 2011

2011-10-19T21:04:58Z

← Older revision		Revision as of 21:04, 19 October 2011
Line 39:		Line 39:

	<h2>The ItemNotPresent methods</h2>		<h2>The ItemNotPresent methods</h2>
	{{Template:~~List of~~ ItemNotPresent ~~methods~~}}		{{Template:Method list header\|class=ItemNotPresent}}
			<div class="showVisit">
			<table class="wikitable">
			<tr><th>Method</th><th>Description</th></tr>
			<tr><td valign="top">[[New (ItemNotPresent constructor)\|New]]</td><td valign="top">Create a new ItemNotPresent object</td></tr>
			</table>
			</div>

	The methods in the class are described in the subsections that follow. In addition:		The methods in the class are described in the subsections that follow. In addition:

Alex at 20:57, 19 October 2011

2011-10-19T20:57:03Z

← Older revision		Revision as of 20:57, 19 October 2011
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	{{Template:ItemNotPresent:New subtitle}}		{{Template:ItemNotPresent:New subtitle}}

	This [[Notation conventions for methods\|callable]] constructor generates an instance of an<var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:		This [[Notation conventions for methods\|callable]] constructor generates an instance of an <var>[[ItemNotPresent_class\|ItemNotPresent]]</var> exception. The <var>New</var> method format follows:

	<h3>Syntax</h3>		<h3>Syntax</h3>

Alex at 20:53, 19 October 2011

2011-10-19T20:53:59Z

← Older revision		Revision as of 20:53, 19 October 2011
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	The class's only method is the <var>[[New_(ItemNotPresent_constructor)\|New]]</var> constructor, which you would typically use with a <var class="product">User Language</var> <var>[[Throw statement\|Throw]]</var> statement to produce an <var>ItemNotPresent</var> exception yourself.		The class's only method is the <var>[[New_(ItemNotPresent_constructor)\|New]]</var> constructor, which you would typically use with a <var class="product">User Language</var> <var>[[Throw statement\|Throw]]</var> statement to produce an <var>ItemNotPresent</var> exception yourself.
	For example:		For example:
	<p class="code">throw %(~~itemNotFound~~):new		<p class="code">throw %(itemNotPresent):new
	</p>		</p>

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	<h4>Syntax terms</h4>		<h4>Syntax terms</h4>
	<table class="syntaxTable">		<table class="syntaxTable">
	<tr><th>%~~itemNotFound~~</th>		<tr><th>%itemNotPresent</th>
	<td>An <var>ItemNotPresent</var> %variable which will refer to the newly created object.		<td>An <var>ItemNotPresent</var> %variable which will refer to the newly created object.
	</td></tr>		</td></tr>