repo_zf1/documentation/manual/pt-br/module_specs/Zend_View-Introduction.xml

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<sect1 id="zend.view.introduction">
    <title>Introdução</title>

    <para>
        <classname>Zend_View</classname> é uma classe para trabalhar com a parte de visualização do
        padrão de projeto MVC. Basicamente ela existe para separar o script de visualização dos
        controladores e modelos. Ela fornece um sistema de assistentes, filtros de saída e escape
        de variáveis.
    </para>

    <para>
        <classname>Zend_View</classname> é um sistema de template agnóstico; você pode usar o
        <acronym>PHP</acronym> como sua linguagem de template, ou criar instâncias de outros
        sistemas de template e manipulá-las dentro do seu script de visualização.
    </para>

    <para>
        Essencialmente, o funcionamento do <classname>Zend_View</classname> acontece em duas etapas
        principais:
        1. Seu script controlador cria uma instância de <classname>Zend_View</classname>,
        atribuindo-lhe variáveis.
        2. O controlador instrui o <classname>Zend_View</classname> a renderizar uma determinada
        visualização, passando o controle ao script de visualização, responsável pela geração da
        saída a ser visualizada.
    </para>

    <sect2 id="zend.view.introduction.controller">
        <title>Script Controlador</title>

        <para>
            Neste exemplo simples, suponhamos que seu controlador tenha uma listagem contendo dados
            sobre livros, que queremos renderizar para uma visualização. O controlador poderia ser
            algo como isto:
        </para>

        <programlisting language="php"><![CDATA[
// use a model to get the data for book authors and titles.
$data = array(
    array(
        'author' => 'Hernando de Soto',
        'title' => 'The Mystery of Capitalism'
    ),
    array(
        'author' => 'Henry Hazlitt',
        'title' => 'Economics in One Lesson'
    ),
    array(
        'author' => 'Milton Friedman',
        'title' => 'Free to Choose'
    )
);

// now assign the book data to a Zend_View instance
Zend_Loader::loadClass('Zend_View');
$view = new Zend_View();
$view->books = $data;

// and render a view script called "booklist.php"
echo $view->render('booklist.php');
]]></programlisting>
    </sect2>

    <sect2 id="zend.view.introduction.view">
        <title>Script Visualizador</title>

        <para>
            Agora necessitaremos do script de visualização associado, "booklist.php". Trata-se de um
            script <acronym>PHP</acronym> como qualquer outro, com uma exceção: ele executa dentro
            do escopo da instância de <classname>Zend_View</classname>, o que implica que as
            referências a $this apontam para as propriedades e métodos da instância
            <classname>Zend_View</classname>. (Variáveis atribuídas à instância pelo controlador são
            propriedades públicas da instância de <classname>Zend_View</classname>). Deste modo, um
            script de visualização muito básico poderia se parecer com isto:
        </para>

        <programlisting language="php"><![CDATA[
 if ($this->books): ?>

    <!-- Uma tabela contendo alguns livros. -->
    <table>
        <tr>
            <th>Autor</th>
            <th>Título</th>
        </tr>

        <?php foreach ($this->books as $key => $val): ?>
        <tr>
            <td><?php echo $this->escape($val['author']) ?></td>
            <td><?php echo $this->escape($val['title']) ?></td>
        </tr>
        <?php endforeach; ?>

    </table>

<?php else: ?>

    <p>Não existem livros a serem exibidos.</p>

<?php endif;?>
]]></programlisting>

        <para>
            Observe a forma como empregamos o método "escape()" para escapar o conteúdo das
            variáveis para a saída.
        </para>
    </sect2>

    <sect2 id="zend.view.introduction.options">
        <title>Options</title>

        <para>
            <classname>Zend_View</classname> has several options that may be set to
            configure the behaviour of your view scripts.
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <property>basePath</property>: indicate a base path from which to set
                    the script, helper, and filter path. It assumes a directory
                    structure of:
                </para>

                <programlisting language="php"><![CDATA[
base/path/
    helpers/
    filters/
    scripts/
]]></programlisting>

                <para>
                    This may be set via <methodname>setBasePath()</methodname>,
                    <methodname>addBasePath()</methodname>, or the <property>basePath</property>
                    option to the constructor.
                </para>
            </listitem>

            <listitem>
                <para>
                    <property>encoding</property>: indicate the character encoding to use
                    with <methodname>htmlentities()</methodname>,
                    <methodname>htmlspecialchars()</methodname>, and other operations. Defaults
                    to UTF-8. May be set via
                    <methodname>setEncoding()</methodname> or the <property>encoding</property>
                    option to the constructor.
                </para>
            </listitem>

            <listitem>
                <para>
                    <property>escape</property>: indicate a callback to be used by
                    <methodname>escape()</methodname>. May be set via
                    <methodname>setEscape()</methodname> or the <property>escape</property> option
                    to the constructor.
                </para>
            </listitem>

            <listitem>
                <para>
                    <property>filter</property>: indicate a filter to use after rendering
                    a view script. May be set via <methodname>setFilter()</methodname>,
                    <methodname>addFilter()</methodname>, or the <property>filter</property> option
                    to the constructor.
                </para>
            </listitem>

            <listitem>
                <para>
                    <property>strictVars</property>: force <classname>Zend_View</classname> to emit
                    notices and warnings when uninitialized view variables are
                    accessed. This may be set by calling
                    <methodname>strictVars(true)</methodname> or passing the
                    <property>strictVars</property> option to the constructor.
                </para>
            </listitem>
        </itemizedlist>
    </sect2>

    <sect2 id="zend.view.introduction.shortTags">
        <title>Short Tags with View Scripts</title>

        <para>
            In our examples, we make use of <acronym>PHP</acronym> long tags:
            <emphasis>&lt;?php</emphasis>. We also favor the use of <ulink
                url="http://us.php.net/manual/en/control-structures.alternative-syntax.php">alternate
                syntax for control structures</ulink>. These are convenient shorthands to use when
            writing view scripts, as they make the constructs more terse, keep statements on single
            lines, and eliminate the need to hunt for brackets within <acronym>HTML</acronym>.
        </para>

        <para>
            In previous versions, we often recommended using short tags (<emphasis>&lt;?</emphasis>
            and <emphasis>&lt;?=</emphasis>), as they make the view scripts slightly less verbose.
            However, the default for the <filename>php.ini</filename>
            <constant>short_open_tag</constant> setting is typically off in production or on shared
            hosts -- making their use not terribly portable. If you use template
            <acronym>XML</acronym> in view scripts, short open tags will cause the templates to fail
            validation. Finally, if you use short tags when <constant>short_open_tag</constant> is
            off, the view scripts will either cause errors or simply echo <acronym>PHP</acronym>
            code back to the viewer.
        </para>

        <para>
            If, despite these warnings, you wish to use short tags but they are disabled, you have
            two options:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    Turn on short tags in your <filename>.htaccess</filename> file:
                </para>

                <programlisting language="apache"><![CDATA[
php_value "short_open_tag" "on"
]]></programlisting>

                <para>
                    This will only be possible if you are allowed to create and
                    utilize <filename>.htaccess</filename> files. This directive can
                    also be added to your <filename>httpd.conf</filename> file.
                </para>
            </listitem>

            <listitem>
                <para>
                    Enable an optional stream wrapper to convert short tags to
                    long tags on the fly:
                </para>

                <programlisting language="php"><![CDATA[
$view->setUseStreamWrapper(true);
]]></programlisting>

                <para>
                    This registers <classname>Zend_View_Stream</classname> as a stream
                    wrapper for view scripts, and will ensure that your code
                    continues to work as if short tags were enabled.
                </para>
            </listitem>
        </itemizedlist>

        <warning>
            <title>View Stream Wrapper Degrades Performance</title>

            <para>
                Usage of the stream wrapper <emphasis>will</emphasis> degrade
                performance of your application, though actual benchmarks are
                unavailable to quantify the amount of degradation. We recommend
                that you either enable short tags, convert your scripts to use
                full tags, or have a good partial and/or full page content
                caching strategy in place.
            </para>
        </warning>
    </sect2>

    <sect2 id="zend.view.introduction.accessors">
        <title>Utility Accessors</title>

        <para>
            Typically, you'll only ever need to call on <methodname>assign()</methodname>,
            <methodname>render()</methodname>, or one of the methods for setting/adding
            filter, helper, and script paths. However, if you wish to extend
            <classname>Zend_View</classname> yourself, or need access to some of its
            internals, a number of accessors exist:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <methodname>getVars()</methodname> will return all assigned variables.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>clearVars()</methodname> will clear all assigned variables;
                    useful when you wish to re-use a view object, but want to
                    control what variables are available.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getScriptPath($script)</methodname> will retrieve the
                    resolved path to a given view script.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getScriptPaths()</methodname> will retrieve all registered
                    script paths.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getHelperPath($helper)</methodname> will retrieve the
                    resolved path to the named helper class.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getHelperPaths()</methodname> will retrieve all registered
                    helper paths.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getFilterPath($filter)</methodname> will retrieve the
                    resolved path to the named filter class.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getFilterPaths()</methodname> will retrieve all registered
                    filter paths.
                </para>
            </listitem>
        </itemizedlist>
    </sect2>
</sect1>
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