<document>
    <body>

        <section name="Examples">

            <p>
                In this example, we are showing part of a page to view and Account object, with an option to
                delete the Account.
            </p>


            <subsection name="Account.java">
                <source><![CDATA[
public class Account
{
    public long id;

    public String userName;
    
}]]></source>
            </subsection>

            <subsection name="ViewAccount.tml">
                <source><![CDATA[
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd">
    <body>
        <h1>View Account #${account.id}</h1>

        <t:beandisplay object="account"/>

        <p>
          [<t:actionlink t:id="delete" context="account.id">delete</t:actionlink>
        </p>
    </body>
</html>
]]></source>

                <p>
                    We store the account's id as
                    <em>event context</em>
                    inside the URL. The account's id will
                    be part of the URL and will be accessible when the event request is later triggered.
                </p>


            </subsection>

            <subsection name="ViewAccount.java">
                <source><![CDATA[
public class ViewAccount
{
    @Persist
    private Account account;

    @InjectPage
    private AccountsSummary accountsSummaryPage;

    @Inject
    private AccountDAO accountDAO;

    public Account getAccount() { return account; }

    Object onActionFromDelete(long accountId)
    {
        accountDAO.delete(accountId);

        accountsSummaryPage.setMessage(String.format("Account #%d has been deleted.", accountId));

        return accountsSummaryPage;
    }
}
]]></source>

                <p>
                    The ActionLink component triggers an "action" event, which is matched by the
                    onActionFromDelete() method. A real application might have other action links on the page, for (say)
                    creating new accounts or other operations, thus we use the component's id ("delete")
                    to ensure that the method is only invoked under the expected circumstances.
                </p>

                <p>
                    Notice how the context (from when the link was rendered) now becomes parameters
                    to the event handler method.
                </p>

                <p>
                    The AccountDAO (data access object) service is responsible for the work, we
                    then set a message on another page (the field for this message should be persistent) and return
                    the page. Tapestry will send a redirect request to the client to display the page.
                </p>


            </subsection>

        </section>

        <section name="Notes">

            <p>
                Rarely, you might need to pass more information in the context. For example, perhaps
                account id is not enought to uniquely identify the Account object in question - hypothetically,
                you may need to include a company id as well as the account id. You can
                build an object array to contain both values:
            </p>
            <p>You can do this in a template using the following syntax:</p>
            <source><![CDATA[
<t:actionlink t:id="delete" context="[account.companyId, account.id]">delete ${company.name} / ${account.id}</t:actionlink>

            ]]>        </source>
            
            <source><![CDATA[
    Object onActionFromDelete(long companyId, long accountId)
    {
        accountDAO.delete(companyId, accountId);

        accountsSummaryPage.setMessage(String.format("Account #%d has been deleted.", accountId));

        return accountsSummaryPage;
    }]]></source>            
            
			<p>
			Alternatively, you can provide a getter which returns an object array.
			</p>
            <source><![CDATA[
    public Object[] getAccountContext()
    {
        return new Object[] { account.companyId, account.id };
    }]]></source>

            <p>
                In the template, this would be referenced as:
            </p>
            <source><![CDATA[
        <p>
          [<t:actionlink t:id="delete" context="accountContext">delete</t:actionlink>
        </p>]]></source>

            <p>
  This pattern was more common in early versions of Tapestry; the older versions of the property
  expression language did not have the ability to create an array on the fly.
</p>
        </section>

    </body>
</document>