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>Capítulo 18. Classes e Objetos(PHP 4)</TD
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>Comparando Objetos</A
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> No PHP 4, objetos são comparados de uma maneira bem simples: Duas instâncias
de objetos são iguais se eles tem os mesmos atributos e valores, e se
de instâncias da mesma classe. Regras similares são aplicadas quando comparando dois
objetos utilizando o operador idêntico (<TT
CLASS="literal"
>===</TT
>).
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> Executando o exemplo abaixo:
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>Exemplo 18-1. Exemplo de comparação de objetos no PHP 4</B
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><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">function </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$bool</font><font color="#007700">) {<br /> if (</font><font color="#0000BB">$bool </font><font color="#007700">=== </font><font color="#0000BB">false</font><font color="#007700">) {<br /> return </font><font color="#DD0000">'FALSE'</font><font color="#007700">;<br /> } else {<br /> return </font><font color="#DD0000">'TRUE'</font><font color="#007700">;<br /> }<br />}<br /><br />function </font><font color="#0000BB">compareObjects</font><font color="#007700">(&</font><font color="#0000BB">$o1</font><font color="#007700">, &</font><font color="#0000BB">$o2</font><font color="#007700">) {<br /> echo </font><font color="#DD0000">'o1 == o2 : '</font><font color="#007700">.</font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">== </font><font color="#0000BB">$o2</font><font color="#007700">).</font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 != o2 : '</font><font color="#007700">.</font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">!= </font><font color="#0000BB">$o2</font><font color="#007700">).</font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 === o2 : '</font><font color="#007700">.</font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">=== </font><font color="#0000BB">$o2</font><font color="#007700">).</font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 !== o2 : '</font><font color="#007700">.</font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">!== </font><font color="#0000BB">$o2</font><font color="#007700">).</font><font color="#DD0000">"\n"</font><font color="#007700">;<br />}<br /><br />class </font><font color="#0000BB">Flag </font><font color="#007700">{<br /> var </font><font color="#0000BB">$flag</font><font color="#007700">;<br /><br /> function </font><font color="#0000BB">Flag</font><font color="#007700">(</font><font color="#0000BB">$flag</font><font color="#007700">=</font><font color="#0000BB">true</font><font color="#007700">) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">flag </font><font color="#007700">= </font><font color="#0000BB">$flag</font><font color="#007700">;<br /> }<br />}<br /><br />class </font><font color="#0000BB">SwitchableFlag </font><font color="#007700">extends </font><font color="#0000BB">Flag </font><font color="#007700">{<br /><br /> function </font><font color="#0000BB">turnOn</font><font color="#007700">() {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">flag </font><font color="#007700">= </font><font color="#0000BB">true</font><font color="#007700">;<br /> }<br /><br /> function </font><font color="#0000BB">turnOff</font><font color="#007700">() {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">flag </font><font color="#007700">= </font><font color="#0000BB">false</font><font color="#007700">;<br /> }<br />}<br /><br /></font><font color="#0000BB">$o </font><font color="#007700">= new </font><font color="#0000BB">Flag</font><font color="#007700">();<br /></font><font color="#0000BB">$p </font><font color="#007700">= new </font><font color="#0000BB">Flag</font><font color="#007700">(</font><font color="#0000BB">false</font><font color="#007700">);<br /></font><font color="#0000BB">$q </font><font color="#007700">= new </font><font color="#0000BB">Flag</font><font color="#007700">();<br /><br /></font><font color="#0000BB">$r </font><font color="#007700">= new </font><font color="#0000BB">SwitchableFlag</font><font color="#007700">();<br /><br />echo </font><font color="#DD0000">"Comparando instâncias criadas com os mesmo parâmetros\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$q</font><font color="#007700">);<br /><br />echo </font><font color="#DD0000">"\nComparando instâncias criadas com parâmetros diferentes\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$p</font><font color="#007700">);<br /><br />echo </font><font color="#DD0000">"\nComparando instâncias de uma classe base com uma classe estendida\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$r</font><font color="#007700">);<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
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><P
>O exemplo acima irá imprimir:</P
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><PRE
CLASS="screen"
>Comparando instâncias criadas com os mesmo parâmetros
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE
Comparando instâncias criadas com parâmetros diferentes
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE
Comparando instâncias de uma classe base com uma classe estendida
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE</PRE
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>
Que é o resultado que esperava-mos obter pelas regras de comparação
acima. Somente instâncias com os mesmos valores de seus atributos e da mesma
classe são considerados iguais e/ou idênticos.
</P
><P
> Mesmo no caso onde temos composição de objetos, as mesmas regras de comparação
se aplicam. No exemplo abaixo, nós criamos uma classe container que preserva
um array associativo de objetos <B
CLASS="classname"
>Flag</B
>.
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><A
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></A
><P
><B
>Exemplo 18-2. Comparação de objetos compostos no PHP 4</B
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><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">class </font><font color="#0000BB">FlagSet </font><font color="#007700">{<br /> var </font><font color="#0000BB">$set</font><font color="#007700">;<br /><br /> function </font><font color="#0000BB">FlagSet</font><font color="#007700">(</font><font color="#0000BB">$flagArr </font><font color="#007700">= array()) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">set </font><font color="#007700">= </font><font color="#0000BB">$flagArr</font><font color="#007700">;<br /> }<br /><br /> function </font><font color="#0000BB">addFlag</font><font color="#007700">(</font><font color="#0000BB">$name</font><font color="#007700">, </font><font color="#0000BB">$flag</font><font color="#007700">) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">set</font><font color="#007700">[</font><font color="#0000BB">$name</font><font color="#007700">] = </font><font color="#0000BB">$flag</font><font color="#007700">;<br /> }<br /><br /> function </font><font color="#0000BB">removeFlag</font><font color="#007700">(</font><font color="#0000BB">$name</font><font color="#007700">) {<br /> if (</font><font color="#0000BB">array_key_exists</font><font color="#007700">(</font><font color="#0000BB">$name</font><font color="#007700">, </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">set</font><font color="#007700">)) {<br /> unset(</font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">set</font><font color="#007700">[</font><font color="#0000BB">$name</font><font color="#007700">]);<br /> }<br /> }<br />}<br /><br /><br /></font><font color="#0000BB">$u </font><font color="#007700">= new </font><font color="#0000BB">FlagSet</font><font color="#007700">();<br /></font><font color="#0000BB">$u</font><font color="#007700">-></font><font color="#0000BB">addFlag</font><font color="#007700">(</font><font color="#DD0000">'flag1'</font><font color="#007700">, </font><font color="#0000BB">$o</font><font color="#007700">);<br /></font><font color="#0000BB">$u</font><font color="#007700">-></font><font color="#0000BB">addFlag</font><font color="#007700">(</font><font color="#DD0000">'flag2'</font><font color="#007700">, </font><font color="#0000BB">$p</font><font color="#007700">);<br /></font><font color="#0000BB">$v </font><font color="#007700">= new </font><font color="#0000BB">FlagSet</font><font color="#007700">(array(</font><font color="#DD0000">'flag1'</font><font color="#007700">=></font><font color="#0000BB">$q</font><font color="#007700">, </font><font color="#DD0000">'flag2'</font><font color="#007700">=></font><font color="#0000BB">$p</font><font color="#007700">));<br /></font><font color="#0000BB">$w </font><font color="#007700">= new </font><font color="#0000BB">FlagSet</font><font color="#007700">(array(</font><font color="#DD0000">'flag1'</font><font color="#007700">=></font><font color="#0000BB">$q</font><font color="#007700">));<br /><br />echo </font><font color="#DD0000">"\nComparando objetos compostos u(o,p) e v(q,p)\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$u</font><font color="#007700">, </font><font color="#0000BB">$v</font><font color="#007700">);<br /><br />echo </font><font color="#DD0000">"\nu(o,p) e w(q)\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$u</font><font color="#007700">, </font><font color="#0000BB">$w</font><font color="#007700">);<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
><P
>O exemplo acima irá imprimir:</P
><TABLE
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><TD
><PRE
CLASS="screen"
>Comparando objetos compostos u(o,p) e v(q,p)
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE
u(o,p) e w(q)
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE</PRE
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