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>章 19. 类与对象（PHP 5）</TD
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><A
NAME="language.oop5.iterations"
>Object Iteration</A
></H1
><P
>
PHP 5 provides a way for objects to be defined so it is possible to iterate
through a list of items, with, for example a <A
HREF="control-structures.foreach.html"
>foreach</A
> statement. By default,
all <A
HREF="language.oop5.visibility.html"
>visible</A
> properties will be used
for the iteration.
</P
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><DIV
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><A
NAME="AEN5956"
></A
><P
><B
>例 19-22. Simple Object Iteration</B
></P
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><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">class </font><font color="#0000BB">MyClass<br /></font><font color="#007700">{<br /> </font><font color="#0000BB">public $var1 </font><font color="#007700">= </font><font color="#DD0000">'value 1'</font><font color="#007700">;<br /> </font><font color="#0000BB">public $var2 </font><font color="#007700">= </font><font color="#DD0000">'value 2'</font><font color="#007700">;<br /> </font><font color="#0000BB">public $var3 </font><font color="#007700">= </font><font color="#DD0000">'value 3'</font><font color="#007700">;<br /><br /> </font><font color="#0000BB">protected $protected </font><font color="#007700">= </font><font color="#DD0000">'protected var'</font><font color="#007700">;<br /> </font><font color="#0000BB">private $private </font><font color="#007700">= </font><font color="#DD0000">'private var'</font><font color="#007700">;<br /><br /> function </font><font color="#0000BB">iterateVisible</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"MyClass::iterateVisible:\n"</font><font color="#007700">;<br /> foreach(</font><font color="#0000BB">$this </font><font color="#007700">as </font><font color="#0000BB">$key </font><font color="#007700">=> </font><font color="#0000BB">$value</font><font color="#007700">) {<br /> print </font><font color="#DD0000">"$key => $value</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br /> }<br /> }<br />}<br /><br /></font><font color="#0000BB">$class </font><font color="#007700">= new </font><font color="#0000BB">MyClass</font><font color="#007700">();<br /><br />foreach(</font><font color="#0000BB">$class </font><font color="#007700">as </font><font color="#0000BB">$key </font><font color="#007700">=> </font><font color="#0000BB">$value</font><font color="#007700">) {<br /> print </font><font color="#DD0000">"$key => $value</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br />}<br />echo </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /><br /><br /></font><font color="#0000BB">$class</font><font color="#007700">-></font><font color="#0000BB">iterateVisible</font><font color="#007700">();<br /><br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
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><TR
><TD
><code><font color="#000000">
var1 => value 1<br />var2 => value 2<br />var3 => value 3<br /><br />MyClass::iterateVisible:<br />var1 => value 1<br />var2 => value 2<br />var3 => value 3<br />protected => protected var<br />private => private var</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><P
> As the output shows, the <A
HREF="control-structures.foreach.html"
>foreach</A
> iterated through all
<A
HREF="language.oop5.visibility.html"
>visible</A
> variables that can be
accessed. To take it a step further you can <CODE
CLASS="varname"
>implement</CODE
> one
of PHP 5's internal <A
HREF="language.oop5.interfaces.html"
>interface</A
> named
<CODE
CLASS="varname"
>Iterator</CODE
>. This allows the object to decide what and how
the object will be iterated.
</P
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CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN5967"
></A
><P
><B
>例 19-23. Object Iteration implementing Iterator</B
></P
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><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">class </font><font color="#0000BB">MyIterator implements Iterator<br /></font><font color="#007700">{<br /> </font><font color="#0000BB">private $var </font><font color="#007700">= array();<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">__construct</font><font color="#007700">(</font><font color="#0000BB">$array</font><font color="#007700">)<br /> {<br /> if (</font><font color="#0000BB">is_array</font><font color="#007700">(</font><font color="#0000BB">$array</font><font color="#007700">)) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">var </font><font color="#007700">= </font><font color="#0000BB">$array</font><font color="#007700">;<br /> }<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">rewind</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"rewinding\n"</font><font color="#007700">;<br /> </font><font color="#0000BB">reset</font><font color="#007700">(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">var</font><font color="#007700">);<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">current</font><font color="#007700">() {<br /> </font><font color="#0000BB">$var </font><font color="#007700">= </font><font color="#0000BB">current</font><font color="#007700">(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">var</font><font color="#007700">);<br /> echo </font><font color="#DD0000">"current: $var</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br /> return </font><font color="#0000BB">$var</font><font color="#007700">;<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">key</font><font color="#007700">() {<br /> </font><font color="#0000BB">$var </font><font color="#007700">= </font><font color="#0000BB">key</font><font color="#007700">(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">var</font><font color="#007700">);<br /> echo </font><font color="#DD0000">"key: $var</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br /> return </font><font color="#0000BB">$var</font><font color="#007700">;<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">next</font><font color="#007700">() {<br /> </font><font color="#0000BB">$var </font><font color="#007700">= </font><font color="#0000BB">next</font><font color="#007700">(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">var</font><font color="#007700">);<br /> echo </font><font color="#DD0000">"next: $var</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br /> return </font><font color="#0000BB">$var</font><font color="#007700">;<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">valid</font><font color="#007700">() {<br /> </font><font color="#0000BB">$var </font><font color="#007700">= </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">current</font><font color="#007700">() !== </font><font color="#0000BB">false</font><font color="#007700">;<br /> echo </font><font color="#DD0000">"valid: </font><font color="#007700">{</font><font color="#DD0000">$var</font><font color="#007700">}\n</font><font color="#DD0000">"</font><font color="#007700">;<br /> return </font><font color="#0000BB">$var</font><font color="#007700">;<br /> }<br />}<br /><br /></font><font color="#0000BB">$values </font><font color="#007700">= array(</font><font color="#0000BB">1</font><font color="#007700">,</font><font color="#0000BB">2</font><font color="#007700">,</font><font color="#0000BB">3</font><font color="#007700">);<br /></font><font color="#0000BB">$it </font><font color="#007700">= new </font><font color="#0000BB">MyIterator</font><font color="#007700">(</font><font color="#0000BB">$values</font><font color="#007700">);<br /><br />foreach (</font><font color="#0000BB">$it </font><font color="#007700">as </font><font color="#0000BB">$a </font><font color="#007700">=> </font><font color="#0000BB">$b</font><font color="#007700">) {<br /> print </font><font color="#DD0000">"$a: $b</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br />}<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
rewinding<br />current: 1<br />valid: 1<br />current: 1<br />key: 0<br />0: 1<br />next: 2<br />current: 2<br />valid: 1<br />current: 2<br />key: 1<br />1: 2<br />next: 3<br />current: 3<br />valid: 1<br />current: 3<br />key: 2<br />2: 3<br />next:<br />current:<br />valid:</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><P
> You can also define your class so that it doesn't have to define
all the <CODE
CLASS="varname"
>Iterator</CODE
> functions by simply implementing
the PHP 5 <CODE
CLASS="varname"
>IteratorAggregate</CODE
> interface.
</P
><TABLE
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CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN5975"
></A
><P
><B
>例 19-24. Object Iteration implementing IteratorAggregate</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
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><TR
><TD
><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">class </font><font color="#0000BB">MyCollection implements IteratorAggregate<br /></font><font color="#007700">{<br /> </font><font color="#0000BB">private $items </font><font color="#007700">= array();<br /> </font><font color="#0000BB">private $count </font><font color="#007700">= </font><font color="#0000BB">0</font><font color="#007700">;<br /><br /> </font><font color="#FF8000">// Required definition of interface IteratorAggregate<br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">getIterator</font><font color="#007700">() {<br /> return new </font><font color="#0000BB">MyIterator</font><font color="#007700">(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">items</font><font color="#007700">);<br /> }<br /><br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">add</font><font color="#007700">(</font><font color="#0000BB">$value</font><font color="#007700">) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">items</font><font color="#007700">[</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">count</font><font color="#007700">++] = </font><font color="#0000BB">$value</font><font color="#007700">;<br /> }<br />}<br /><br /></font><font color="#0000BB">$coll </font><font color="#007700">= new </font><font color="#0000BB">MyCollection</font><font color="#007700">();<br /></font><font color="#0000BB">$coll</font><font color="#007700">-></font><font color="#0000BB">add</font><font color="#007700">(</font><font color="#DD0000">'value 1'</font><font color="#007700">);<br /></font><font color="#0000BB">$coll</font><font color="#007700">-></font><font color="#0000BB">add</font><font color="#007700">(</font><font color="#DD0000">'value 2'</font><font color="#007700">);<br /></font><font color="#0000BB">$coll</font><font color="#007700">-></font><font color="#0000BB">add</font><font color="#007700">(</font><font color="#DD0000">'value 3'</font><font color="#007700">);<br /><br />foreach (</font><font color="#0000BB">$coll </font><font color="#007700">as </font><font color="#0000BB">$key </font><font color="#007700">=> </font><font color="#0000BB">$val</font><font color="#007700">) {<br /> echo </font><font color="#DD0000">"key/value: </font><font color="#007700">[</font><font color="#DD0000">$key -> $val</font><font color="#007700">]\n\n</font><font color="#DD0000">"</font><font color="#007700">;<br />}<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
rewinding<br />current: value 1<br />valid: 1<br />current: value 1<br />key: 0<br />key/value: [0 -> value 1]<br /><br />next: value 2<br />current: value 2<br />valid: 1<br />current: value 2<br />key: 1<br />key/value: [1 -> value 2]<br /><br />next: value 3<br />current: value 3<br />valid: 1<br />current: value 3<br />key: 2<br />key/value: [2 -> value 3]<br /><br />next:<br />current:<br />valid:</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
For more examples of iterators, see the
<A
HREF="ref.spl.html"
>SPL Extension</A
>.
</P
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