repo_zf1/documentation/manual/es/module_specs/Zend_Db_Table_Rowset.xml

<sect1 id="zend.db.table.rowset">

    <title>Zend_Db_Table_Rowset</title>

    <sect2 id="zend.db.table.rowset.introduction">

        <title>Introduction</title>

        <para>
            When you run a query against a Table class using the <code>find()</code> or <code>fetchAll()</code>
            methods, the result is returned in an object of type <code>Zend_Db_Table_Rowset_Abstract</code>. A Rowset
            contains a collection of objects descending from <code>Zend_Db_Table_Row_Abstract</code>. You can iterate
            through the Rowset and access individual Row objects, reading or modifying data in the Rows.
        </para>

    </sect2>

    <sect2 id="zend.db.table.rowset.fetch">

        <title>Fetching a Rowset</title>

        <para>
            <code>Zend_Db_Table_Abstract</code> provides methods <code>find()</code> and <code>fetchAll()</code>, each
            of which returns an object of type <code>Zend_Db_Table_Rowset_Abstract</code>.
        </para>

        <example id="zend.db.table.rowset.fetch.example">

            <title>Example of fetching a rowset</title>

            <programlisting role="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll("bug_status = 'NEW'");
]]>
            </programlisting>

        </example>

    </sect2>

    <sect2 id="zend.db.table.rowset.rows">

        <title>Retrieving Rows from a Rowset</title>

        <para>
            The Rowset itself is usually less interesting than the Rows that it contains. This section illustrates how
            to get the Rows that comprise the Rowset.
        </para>

        <para>
            A legitimate query returns zero rows when no rows in the database match the query conditions. Therefore, a
            Rowset object might contain zero Row objects. Since <code>Zend_Db_Table_Rowset_Abstract</code> implements
            the <code>Countable</code> interface, you can use <code>count()</code> to determine the number of Rows in
            the Rowset.
        </para>

        <example id="zend.db.table.rowset.rows.counting.example">

            <title>Counting the Rows in a Rowset</title>

            <programlisting role="php"><![CDATA[
$rowset   = $bugs->fetchAll("bug_status = 'FIXED'");

$rowCount = count($rowset);

if ($rowCount > 0) {
    echo "found $rowCount rows";
} else {
    echo 'no rows matched the query';
}
]]>
            </programlisting>

        </example>

        <example id="zend.db.table.rowset.rows.current.example">

            <title>Reading a Single Row from a Rowset</title>

            <para>
                The simplest way to access a Row from a Rowset is to use the <code>current()</code> method. This is
                particularly appropriate when the Rowset contains exactly one Row.
            </para>

            <programlisting role="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll("bug_id = 1");
$row    = $rowset->current();
]]>
            </programlisting>

        </example>

        <para>
            If the Rowset contains zero rows, <code>current()</code> returns
            PHP's <code>null</code> value.
        </para>

        <example id="zend.db.table.rowset.rows.iterate.example">

            <title>Iterating through a Rowset</title>

            <para>
                Objects descending from <code>Zend_Db_Table_Rowset_Abstract</code> implement the <code>SeekableIterator</code>
                interface, which means you can loop through them using the <code>foreach</code> construct. Each value
                you retrieve this way is a <code>Zend_Db_Table_Row_Abstract</code> object that corresponds to one
                record from the table.
            </para>

            <programlisting role="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->fetchAll();

foreach ($rowset as $row) {

    // output 'Zend_Db_Table_Row' or similar
    echo get_class($row) . "\n";

    // read a column in the row
    $status = $row->bug_status;

    // modify a column in the current row
    $row->assigned_to = 'mmouse';

    // write the change to the database
    $row->save();
}
]]>
            </programlisting>

        </example>

         <example id="zend.db.table.rowset.rows.seek.example">

            <title>Seeking to a known position into a Rowset</title>

            <para>
                <code>SeekableIterator</code> allows you to seek to a position that you would like the iterator to jump to.
                Simply use the <code>seek()</code> method for that. Pass it an integer representing the number of the Row
                you would like your Rowset to point to next, don't forget that it starts with index 0. If the index is wrong,
                ie doesn't exist, an exception will be thrown. You should use <code>count()</code> to check the number of
                results before seeking to a position.
            </para>

            <programlisting role="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->fetchAll();

// takes the iterator to the 9th element (zero is one element) :
$rowset->seek(8);

// retrive it
$row9 = $rowset->current();

// and use it
$row9->assigned_to = 'mmouse';
$row9->save();
]]>
            </programlisting>

        </example>

            <para>
                <code>getRow()</code> allows you to get a specific row in the Rowset, knowing its position; don't forget
                however that positions start with index zero. The first parameter for <code>getRow()</code> is an integer
                for the position asked. The second optional parameter is a boolean; it tells the Rowset iterator if it must
                seek to that position in the same time, or not (default is false). This method returns a Zend_Db_Table_Row
                object by default. If the position requested does not exist, an exception will be thrown. Here is an example :
            </para>

            <programlisting role="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->fetchAll();

// retrieve the 9th element immediately:
$row9->getRow(8);

// and use it:
$row9->assigned_to = 'mmouse';
$row9->save();
]]>
            </programlisting>



        <para>
            After you have access to an individual Row object, you can manipulate the Row using methods described in
            <xref linkend="zend.db.table.row" />.
        </para>

    </sect2>

    <sect2 id="zend.db.table.rowset.to-array">

        <title>Retrieving a Rowset as an Array</title>

        <para>
            You can access all the data in the Rowset as an array using the <code>toArray()</code> method of the Rowset
            object. This returns an array containing one entry per Row. Each entry is an associative array having keys
            that correspond to column names and elements that correspond to the respective column values.
        </para>

        <example id="zend.db.table.rowset.to-array.example">

            <title>Using toArray()</title>

            <programlisting role="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll();

$rowsetArray = $rowset->toArray();

$rowCount = 1;
foreach ($rowsetArray as $rowArray) {
    echo "row #$rowCount:\n";
    foreach ($rowArray as $column => $value) {
        echo "\t$column => $value\n";
    }
    ++$rowCount;
    echo "\n";
}
]]>
            </programlisting>
        </example>

        <para>
            The array returned from <code>toArray()</code> is not updateable. That is, you can modify values in the
            array as you can with any array, but changes to the array data are not propagated to the database.
        </para>

    </sect2>

    <sect2 id="zend.db.table.rowset.serialize">

        <title>Serializing and Unserializing a Rowset</title>

        <para>
            Objects of type <code>Zend_Db_Table_Rowset_Abstract</code> are serializable. In a similar fashion to
            serializing an individual Row object, you can serialize a Rowset and unserialize it later.
        </para>

        <example id="zend.db.table.rowset.serialize.example.serialize">

            <title>Serializing a Rowset</title>

            <para>
                Simply use PHP's <code>serialize()</code> function to create a string containing a byte-stream
                representation of the Rowset object argument.
            </para>

            <programlisting role="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll();

// Convert object to serialized form
$serializedRowset = serialize($rowset);

// Now you can write $serializedRowset to a file, etc.
]]>
            </programlisting>

        </example>

        <example id="zend.db.table.rowset.serialize.example.unserialize">

            <title>Unserializing a Serialized Rowset</title>

            <para>
                Use PHP's <code>unserialize()</code> function to restore a string containing a byte-stream
                representation of an object.  The function returns the original object.
            </para>

            <para>
                Note that the Rowset object returned is in a <emphasis>disconnected</emphasis> state. You can iterate
                through the Rowset and read the Row objects and their properties, but you cannot change values in the
                Rows or execute other methods that require a database connection (for example, queries against related
                tables).
            </para>

            <programlisting role="php"><![CDATA[
$rowsetDisconnected = unserialize($serializedRowset);

// Now you can use object methods and properties, but read-only
$row = $rowsetDisconnected->current();
echo $row->bug_description;
]]>
            </programlisting>

        </example>

        <note>
            <title>Why do Rowsets unserialize in a disconnected state?</title>
            <para>
                A serialized object is a string that is readable to anyone who possesses it. It could be a security
                risk to store parameters such as database account and password in plain, unencrypted text in the
                serialized string. You would not want to store such data to a text file that is not protected, or send
                it in an email or other medium that is easily read by potential attackers. The reader of the serialized
                object should not be able to use it to gain access to your database without knowing valid credentials.
            </para>
        </note>

        <para>
            You can reactivate a disconnected Rowset using the <code>setTable()</code> method.  The argument to this
            method is a valid object of type <code>Zend_Db_Table_Abstract</code>, which you create.  Creating a Table
            object requires a live connection to the database, so by reassociating the Table with the Rowset, the
            Rowset gains access to the database.  Subsequently, you can change values in the Row objects contained in
            the Rowset and save the changes to the database.
        </para>

        <example id="zend.db.table.rowset.serialize.example.set-table">

            <title>Reactivating a Rowset as Live Data</title>

            <programlisting role="php"><![CDATA[
$rowset = unserialize($serializedRowset);

$bugs = new Bugs();

// Reconnect the rowset to a table, and
// thus to a live database connection
$rowset->setTable($bugs);

$row = $rowset->current();

// Now you can make changes to the row and save them
$row->bug_status = 'FIXED';
$row->save();
]]>
            </programlisting>

        </example>

        <para>
            Reactivating a Rowset with <code>setTable()</code> also reactivates all the Row objects contained in that
            Rowset.
        </para>

    </sect2>

    <sect2 id="zend.db.table.rowset.extending">

        <title>Extending the Rowset class</title>

        <para>
            You can use an alternative concrete class for instances of Rowsets
            by extending Zend_Db_Table_Rowset_Abstract.  Specify the custom
            Rowset class by name either in the <code>$_rowsetClass</code>
            protected member of a Table class, or in the array argument of the
            constructor of a Table object.
        </para>

        <example id="zend.db.table.rowset.extending.example">
            <title>Specifying a custom Rowset class</title>
            <programlisting role="php"><![CDATA[
class MyRowset extends Zend_Db_Table_Rowset_Abstract
{
    // ...customizations
}

// Specify a custom Rowset to be used by default
// in all instances of a Table class.
class Products extends Zend_Db_Table_Abstract
{
    protected $_name = 'products';
    protected $_rowsetClass = 'MyRowset';
}

// Or specify a custom Rowset to be used in one
// instance of a Table class.
$bugs = new Bugs(array('rowsetClass' => 'MyRowset'));
]]>
            </programlisting>
        </example>

        <para>
            Typically, the standard Zend_Db_Rowset concrete class is
            sufficient for most usage.  However, you might find it useful
            to add new logic to a Rowset, specific to a given Table.
            For example, a new method could calculate an aggregate
            over all the Rows in the Rowset.
        </para>

        <example id="zend.db.table.rowset.extending.example-aggregate">
            <title>Example of Rowset class with a new method</title>
            <programlisting role="php"><![CDATA[
class MyBugsRowset extends Zend_Db_Table_Rowset_Abstract
{
    /**
     * Find the Row in the current Rowset with the
     * greatest value in its 'updated_at' column.
     */
    public function getLatestUpdatedRow()
    {
        $max_updated_at = 0;
        $latestRow = null;
        foreach ($this as $row) {
            if ($row->updated_at > $max_updated_at) {
                $latestRow = $row;
            }
        }
        return $latestRow;
    }
}

class Bugs extends Zend_Db_Table_Abstract
{
    protected $_name = 'bugs';
    protected $_rowsetClass = 'MyBugsRowset';
}
]]>
            </programlisting>
        </example>

    </sect2>


</sect1>
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