📄 classes, objects, and ties.mht

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Subject: Classes, Objects, and Ties
Date: Wed, 29 Apr 2009 09:27:23 +0800
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<H1 class=3DSECT1><A name=3DCLASSESETC>13. Classes, Objects, and =
Ties</A></H1>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN704>Introduction</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT>$object =3D <FONT color=3D#00ffff>{};</FONT>                      =
 <FONT color=3D#bebebe># hash reference
</FONT><FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$object, <FONT =
color=3D#00cd00>"Data::Encoder"</FONT><FONT color=3D#00ffff>);</FONT>    =
<FONT color=3D#bebebe># bless $object into Data::Encoder class
</FONT><FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$object<FONT color=3D#00ffff>);</FONT>           =
          <FONT color=3D#bebebe># bless $object into current package
#-----------------------------
</FONT>$obj =3D <FONT color=3D#00ffff>[</FONT><FONT =
color=3D#cdcd00>3</FONT>,<FONT color=3D#cdcd00>5</FONT><FONT =
color=3D#00ffff>];</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#98fb98>ref</FONT><FONT =
color=3D#00ffff>(</FONT>$obj<FONT color=3D#00ffff>)</FONT>, <FONT =
color=3D#00cd00>" "</FONT>, $obj-&gt;<FONT color=3D#00ffff>[</FONT><FONT =
color=3D#cdcd00>1</FONT><FONT color=3D#00ffff>]</FONT>, <FONT =
color=3D#00cd00>"\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#98fb98>bless</FONT><FONT color=3D#00ffff>(</FONT>$obj, =
<FONT color=3D#00cd00>"Human::Cannibal"</FONT><FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#98fb98>ref</FONT><FONT =
color=3D#00ffff>(</FONT>$obj<FONT color=3D#00ffff>)</FONT>, <FONT =
color=3D#00cd00>" "</FONT>, $obj-&gt;<FONT color=3D#00ffff>[</FONT><FONT =
color=3D#cdcd00>1</FONT><FONT color=3D#00ffff>]</FONT>, <FONT =
color=3D#00cd00>"\n"</FONT><FONT color=3D#00ffff>;</FONT>

ARRAY <FONT color=3D#cdcd00>5</FONT>

Human::Cannibal <FONT color=3D#cdcd00>5</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$obj-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>Stomach</FONT><FONT color=3D#00ffff>}</FONT> =3D <FONT =
color=3D#00cd00>"Empty"</FONT><FONT color=3D#00ffff>;</FONT>   <FONT =
color=3D#bebebe># directly accessing an object's contents
</FONT>$obj-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>NAME</FONT><FONT color=3D#00ffff>}</FONT>    =3D <FONT =
color=3D#00cd00>"Thag"</FONT><FONT color=3D#00ffff>;</FONT>        <FONT =
color=3D#bebebe># uppercase field name to make it stand out (optional)
#-----------------------------
</FONT>$encoded =3D $object-&gt;encode<FONT =
color=3D#00ffff>(</FONT><FONT color=3D#00cd00>"data"</FONT><FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$encoded =3D Data::Encoder-&gt;encode<FONT =
color=3D#00ffff>(</FONT><FONT color=3D#00cd00>"data"</FONT><FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$class</FONT> =
=3D <FONT color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$self</FONT>  =
=3D <FONT color=3D#00ffff>{};</FONT>         <FONT color=3D#bebebe># =
allocate new hash for object
</FONT>    <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$self, $class<FONT color=3D#00ffff>);</FONT>
    <FONT color=3D#ffa500>return</FONT> $self<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$object =3D Class-&gt;new<FONT color=3D#00ffff>();</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$object =3D Class::new<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#00cd00>"Class"</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>class_only_method</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$class</FONT> =
=3D <FONT color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>die</FONT> <FONT color=3D#00cd00>"class method =
called on object"</FONT> <FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#98fb98>ref</FONT> $class<FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#bebebe># more code here
</FONT><FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>instance_only_method</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$self</FONT> =
=3D <FONT color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>die</FONT> <FONT color=3D#00cd00>"instance =
method called on class"</FONT> <FONT color=3D#ffa500>unless</FONT> <FONT =
color=3D#98fb98>ref</FONT> $self<FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#bebebe># more code here
</FONT><FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$lector =3D new Human::Cannibal<FONT color=3D#00ffff>;</FONT>
feed $lector <FONT color=3D#00cd00>"Zak"</FONT><FONT =
color=3D#00ffff>;</FONT>
move $lector <FONT color=3D#00cd00>"New York"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$lector =3D Human::Cannibal-&gt;
new<FONT color=3D#00ffff>();</FONT>

$lector-&gt;feed<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#00cd00>"Zak"</FONT><FONT color=3D#00ffff>);</FONT>
$lector-&gt;move<FONT color=3D#00ffff>(</FONT><FONT color=3D#00cd00>"New =
York"</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ff7f50>printf</FONT> STDERR <FONT =
color=3D#00cd00>"stuff here\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>move $obj-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>FIELD</FONT><FONT color=3D#00ffff>};</FONT>              =
   <FONT color=3D#bebebe># probably wrong
</FONT>move <FONT color=3D#cdad00>$ary</FONT><FONT =
color=3D#00ffff>[</FONT>$i<FONT color=3D#00ffff>];</FONT>                =
      <FONT color=3D#bebebe># probably wrong
#-----------------------------
</FONT>$obj-&gt;move-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>FIELD</FONT><FONT color=3D#00ffff>};</FONT>              =
  <FONT color=3D#bebebe># Surprise!
</FONT>$ary-&gt;move-&gt;<FONT color=3D#00ffff>[</FONT>$i<FONT =
color=3D#00ffff>];</FONT>                   <FONT color=3D#bebebe># =
Surprise!
#-----------------------------
</FONT>$obj-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>FIELD</FONT><FONT color=3D#00ffff>}</FONT>-&gt;
move<FONT color=3D#00ffff>()</FONT>
<FONT color=3D#00ffff>;</FONT>              <FONT color=3D#bebebe># =
Nope, you wish
</FONT><FONT color=3D#cdad00>$ary</FONT><FONT =
color=3D#00ffff>[</FONT>$i<FONT color=3D#00ffff>]</FONT>-&gt;
move<FONT color=3D#00ffff>;</FONT>
                     <FONT color=3D#bebebe># Nope, you wish
#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN707>Constructing an Object</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$class</FONT> =
=3D <FONT color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$self</FONT>  =
=3D <FONT color=3D#00ffff>{</FONT> <FONT color=3D#00ffff>};</FONT>
    <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$self, $class<FONT color=3D#00ffff>);</FONT>
    <FONT color=3D#ffa500>return</FONT> $self<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT> <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT> <FONT color=3D#00ffff>{</FONT> <FONT =
color=3D#00ffff>}</FONT>, <FONT color=3D#ff7f50>shift</FONT> <FONT =
color=3D#00ffff>)</FONT> <FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT> <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>({})</FONT> <FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$self</FONT> =
=3D <FONT color=3D#00ffff>{</FONT> <FONT color=3D#00ffff>};</FONT>  =
<FONT color=3D#bebebe># allocate anonymous hash
</FONT>    <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$self<FONT color=3D#00ffff>);</FONT>
    <FONT color=3D#bebebe># init two sample attributes/data =
members/fields
</FONT>    $self-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>START</FONT><FONT color=3D#00ffff>}</FONT> =3D <FONT =
color=3D#98fb98>time</FONT><FONT color=3D#00ffff>();</FONT><FONT =
color=3D#43cd80>  </FONT>
    $self-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>AGE</FONT><FONT color=3D#00ffff>}</FONT>   =3D <FONT =
color=3D#cdcd00>0</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>return</FONT> $self<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT color=3D#b2dfee>new</FONT> =
<FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#9ac0cd>$classname</FONT>  =3D <FONT =
color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>         <FONT =
color=3D#bebebe># What class are we constructing?
</FONT>    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#9ac0cd>$self</FONT>      =3D <FONT color=3D#00ffff>{};</FONT>   =
          <FONT color=3D#bebebe># Allocate new memory
</FONT>    <FONT color=3D#98fb98>bless</FONT><FONT =
color=3D#00ffff>(</FONT>$self, $classname<FONT color=3D#00ffff>);</FONT> =
      <FONT color=3D#bebebe># Mark it of the right type
</FONT>    $self-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>START</FONT><FONT color=3D#00ffff>}</FONT>  =3D<FONT =
color=3D#43cd80> </FONT>
<FONT color=3D#98fb98>time</FONT><FONT color=3D#00ffff>();</FONT>
       <FONT color=3D#bebebe># init data fields
</FONT>    $self-&gt;<FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>AGE</FONT><FONT color=3D#00ffff>}</FONT>    =3D<FONT =
color=3D#43cd80> </FONT>
<FONT color=3D#cdcd00>0</FONT><FONT color=3D#00ffff>;</FONT>

    <FONT color=3D#ffa500>return</FONT> $self<FONT =
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