## Templating an Existing Tcl Page

Templating System : Migration

### In a Nutshell

When templatizing a legacy tcl page, your task is to separate code and graphical presentation. The latter goes into an ADP file; it contains essentially HTML, augmented by a few special tags and the `@variable@` construct. The code goes into a Tcl script. In other words, a templated page consists of two files, a Tcl part that puts its results in data sources, and an ADP page (the template), into which these data sources will be interpolated to yield a complete HTML page.

### General

As usual, the Tcl page should start with a call to `ad_page_contract`. In its `-properties` block you promise the data sources that your script will provide; they were earlier called page properties, hence the name of the option. Then your script performs all the computations and queries needed to define these data sources. There are special mechanisms for handling multirow data sources; see below.

At the end of the Tcl script, you should call `ad_return_template`. The template runs after the tcl script, and can use these data sources.

Make sure that the fancy adp parser is enabled in your AOL ini file.

          [ns/server/myserver/adp]
          DefaultParser=fancy

A few more hints

- Do not write to the connection directly. Avoid `ns_puts`, `ns_write` etc., which don't wait till the headers are written or the page is completed; they may act differently than you expect.
- If you can, put code in the tcl file, not between `<% %>` in the adp page.
- Put HTML in the adp page, not int the tcl program. Put reusable HTML fragments in a separate adp file (think of it as a widget) that will be `<include>`d from several pages. Prefer this to writing a tcl proc that returns HTML.
- Remember to remove backslashes where you had to escape special characters, as in

  >     Nuts  \$2.70 \[<a href=\"shoppe\">buy</a>\]

### Forms

There is nothing special about building forms; just use the `<form>` tag as always. All HTML tags can be used in the ADP file (template).

### A simple page

First I take a page from the news package as an example. For simplicity, I pick `item-view`, which does not use a `<form>`. I reformatted it a bit to make three panes fit next to each other and to line up corresponding code.

old tcl code | new
--- | ---
`packages/news/www/item-view.tcl` | `packages/news/www/item-view.adp`

    # /packages/news/admin/index.tcl
    ad_page_contract {

        View a news item.

        @author Jon Salz (jsalz@arsdigita.com)
        @creation-date 11 Aug 2000
        @cvs-id $Id$

    } {
        news_item_id:integer,notnull
    }

    db_1row news_item_select {
        select *
        from news_items
        where news_item_id = :news_item_id
    }

    set body "
    [ad_header $title]
    <h2>$title</h2>
    [ad_context_bar [list "" "News"] $title]

    <hr>

    <p>Released $release_date:

    <blockquote>
    $body
    </blockquote>

    [ad_footer]
    "

    doc_return 200 text/html $body
    return

    ad_page_contract {

        View a news item.

        @author Jon Salz (jsalz@arsdigita.com)
        @creation-date 11 Aug 2000
        @cvs-id $Id$

    } {
        news_item_id:integer,notnull
    } -properties {
      body:onevalue
      release_date:onevalue
      title:onevalue
      header:onevalue
      context_bar:onevalue
      footer:onevalue
    }

    db_1row news_item_select {
        select *
        from news_items
        where news_item_id = :news_item_id
    }

    set context_bar [ad_context_bar \
        [list "" "News"] $title]

    ad_return_template

    <master>
    <property name="doc(title)">@title@</property>
    <property name="context">@context;noquote@</property>

    <hr>

    <p>Released @release_date@:

    <blockquote>
    @body@
    </blockquote>

### Multi-Row Data Sources

Technically, the result of a query that may return multiple rows is stored in several arrays. This datasource is filled by a call to `db_multirow`, and the repeating part of the HTML output is produced by the `<multiple>` tag. The following example shows the part of the `index` page of the News module that uses the mechanism, not a whole page.

old tcl code | new
--- | ---
`packages/news/www/index.tcl` | `packages/news/www/index.adp`

    ad_page_contract {

        Displays a list of
        available news items.

        @param archive_p show archived
                          news items?
        @author Jon Salz (jsalz@mit.edu)
        @creation-date 11 Aug 2000
        @cvs-id $Id$
    } {
    }

    ad_page_contract {

        Displays a list of available
        news items.

        @param archive_p show archived
                          news items?
        @author Jon Salz (jsalz@mit.edu)
        @creation-date 11 Aug 2000
        @cvs-id $Id$
    } {
    } -properties {
      header:onevalue
      context_bar:onevalue
      subsite_id:onevalue
      subsite:multirow
      item:multirow
      footer:onevalue
    }

... | ... | ...

    append body "
    <ul>
    "

    db_foreach news_items_select {
        select news_item_id, title
        from news_items_obj
        where context_id = :subsite_id
        and sysdate >= release_date
        and (   expiration_date is null
             or expiration_date > sysdate)
    } {
        append body "<li><a href=
    	\"item-view?news_item_id="\
    	"$news_item_id\"
    	>$title</a>\n"

    } if_no_rows {
        append body "<li>There are
            currently no news items
            available.\n"
    }

    append body "
    <p><li>You can use the <a href=
        \"admin/\">administration
        interface</a> to post a new
        item (there's currently no
        security in place).

    </ul>
    "

    db_multirow item news_items_select {
        select news_item_id, title
        from news_items_obj
        where context_id = :subsite_id
        and sysdate >= release_date
        and (   expiration_date is null
             or expiration_date > sysdate)
    }

    <ul>

    <multiple name=item>

      <li><a href=
          "item-view?news_item_id=<%
          %>@item.news_item_id@"
          >@item.title@</a>
    </multiple>

    <if @item:rowcount@ eq 0>
      <li>There are
      currently no news items
      available.
    </if>

    <p><li>You can use the <a href=
      "admin/">administration
      interface</a> to post a new
      item (there's currently no
      security in place).

    </ul>

Notes:

- I use the general `<if>` construct to handle the case when no lines are returned. (The `<multiple>` loop just executes zero times.)
- For a list of the available tags, refer to the templating documentation.
- Blue color marks additional syntax necessary to wrap lines short.
- The proc `db_multirow` does have a code block and an optional `if_no_rows` block, just like `db_foreach`. They aren't used in the example, though.

If you have a more complicated db_foreach, where logic is performed inside the body, then it might be helpful to build your own multirow variable. In the excert below, taken from /pvt/alerts.tcl and /pvt/alerts.adp, the foreach logic made it hard to use the db_multirow because it needed a combination of the output from sql and also the output of tcl procedures using that value.

old tcl code | new
--- | ---
`packages/acs-core-ui/www/pvt/alerts.tcl` | `packages/acs-core-ui/www/pvt/alerts.adp`

    ad_page_contract {
        @cvs-id $Id$
    } {
    }

    ad_page_contract {
        @cvs-id $Id$
    } {
    } -properties {
        header:onevalue
        decorate_top:onevalue
        ad_footer:onevalue
        discussion_forum_alert_p:onevalue
        bboard_keyword_p:onevalue
        bboard_rows:multirow
        classified_email_alert_p:onevalue
        classified_rows:multirow
        gc_system_name:onevalue
    }

... | ... | ...

    if { [db_table_exists "bboard_email_alerts"] } {

     set counter 0

     db_foreach alerts_list "
     select bea.valid_p, bea.frequency,
            bea.keywords, bt.topic, bea.rowid
     from bboard_email_alerts bea, bboard_topics bt
     where bea.user_id = :user_id
     and bea.topic_id = bt.topic_id
     order by bea.frequency" {
       incr counter

       if { $valid_p == "f" } {
         # alert has been disabled
         set status "Disabled"
         set action "
         <a href=\"/bboard/alert-reenable\">
         Re-enable</a>"
       } else {
         # alert is enabled
         set status "
         <font color=red>Enabled</font>"
         set action "
         <a href=\"/bboard/alert-disable\">
         Disable</a>"
       }

       append existing_alert_rows "<tr>
       <td>$status</td>
       <td>$action</td>
       <td>$topic</td>
       <td>$frequency</td>"

       if { [bboard_pls_blade_installed_p] == 1 } {
         append existing_alert_rows "
         <td>\"$keywords\"</td>"
       }
       append existing_alert_rows "</tr>\n"

     }

     if  { $counter > 0 } {
       set wrote_something_p 1
       set keyword_header ""
       if { [bboard_pls_blade_installed_p] == 1 } {
         set keyword_header "<th>Keywords</th>"
       }
       append page_content "
       <h3>Your discussion forum alerts</h3>

       <blockquote>
       <table>
       <tr>
       <th>Status</th>
       <th>Action</th>
       <th>Topic</th>
       <th>Frequency</th>
       $keyword_header
       </tr>

       $existing_alert_rows
       </table>
       </blockquote>
       "
     }
    }

    set discussion_forum_alert_p 0

    if { [db_table_exists "bboard_email_alerts"] } {
      set discussion_forum_alert_p 1

      set rownum 0

      if { [bboard_pls_blade_installed_p] == 1 } {
        set bboard_keyword_p 1
      } else {
        set bboard_keyword_p 0
      }

      db_foreach alerts_list "
      select bea.valid_p, bea.frequency,
             bea.keywords, bt.topic, bea.rowid
      from bboard_email_alerts bea, bboard_topics bt
      where bea.user_id = :user_id
      and bea.topic_id = bt.topic_id
      order by bea.frequency" {
      incr rownum

      if { $valid_p == "f" } {
        # alert has been disabled for some reason
        set bboard_rows:[set rownum](status) "disable"
        set bboard_rows:[set rownum](action_url) "
        /bboard/alert-reenable"
      } else {
        # alert is enabled
        set bboard_rows:[set rownum](status) "enable"
        set bboard_rows:[set rownum](action_url) "
        /bboard/alert-disable"
      }

      set bboard_rows:[set rownum](topic) $topic
      set bboard_rows:[set rownum](frequency) $frequency
      set bboard_rows:[set rownum](keywords) $keywords

      } if_no_rows {
        set discussion_forum_alert_p 0
      }
      set bboard_rows:rowcount $rownum

    }

    <if @discussion_forum_alert_p@ eq 1>

    <h3>Your discussion forum alerts</h3>

    <blockquote>
       <table>
       <tr><th>Status</th>
           <th>Action</th>
           <th>Topic</th>
           <th>Frequency</th>
         <if @bboard_keyword_p@ eq 1>
           <th>Keyword</th>
         </if>
       </tr>
     <multiple name=bboard_rows>

       <tr>
          <if @bboard_rows.status@ eq "enabled">
           <td><font color=red>Enabled</font></td>
           <td><a href="@bboard_rows.action_url@">
           Disable</a></td>
          </if>
          <else>
           <td>Disabled</td>
           <td><a href="@bboard_rows.action_url@">
           Re-enable</a></td>
          </else>
           <td>@bboard_rows.topic@</td>
           <td>@bboard_rows.frequency@</td>
         <if @bboard_rows.bboard_keyword_p@ eq 1>
           <td>@keyword</td>
         </if>
       </tr>

     </multiple>
       </table>
    </blockquote>

    </if>

Last modified: $Id$