HTML was created as a static content markup language. But the true power of the Web today lies in the ability to dynamically modify web page content on demand. This has normally required learning server-side scripting languages with steep learning curves like Perl or PHP. In mid-2009 RunRev released the first version of its server-side LiveCode scripting module, known officially as LiveCode Server. What this means is that LiveCode, formerly confined to scripting in the LiveCode stack environment, can be used to create powerful, dynamic web pages.
One way to get access to LiveCode server-side scripting is to purchase a subscription to the On-rev web hosting service, a full-featured service that includes many standard hosting features, and includes a fully-integrated LiveCode Server capability. You can also download the open-source "community" version of LiveCode Server from http://downloads.livecode.com/livecode/. Once downloaded, LiveCode Server must be installed on your web server. Installation instructions are included in the download.
For this class, LiveCode Server has been set up on the hummac server, the same server that hosts the class file server and the MySQL server we have been using. You must have a login account on this server to log in. (For registered students in DigHT courses the login information was given in class or sent to you separately.)
First we will look at the basics of server-side LiveCode scripting. We will use BBedit, but the same could be done using any plain text editor and SFTP client. BBedit is convenient because it has a built-in SFTP client that allows us to work in a single environment.
<?lc LiveCode code here ?>
The opening and closing tags can be on different lines, but all LiveCode statements must be enclosed by these tags.
Type a simple LiveCode statement between the lc tags:
<?lc put "Hello world." ?>
Save your document.
What do we learn from this very simple example?
putstatement without a destination container specified is output directly to the web page.
One more important concept: .lc documents are simply specialized HTML documents. They can contain any valid HTML code, interspersed with any number of
<?lc ?> tags. LiveCode server documents can have lots of HTML code in them, or they can be written to simply return plain text strings.
Assignment: Look at some simple examples on the on-rev web site before the next class period. Look at the first five topics: Introduction, Basics, URL Get, Form, and Database. You should understand and try out most of these scripts.
Clearly, the simple example we used above is boring and doesn't give any advantage over plain HTML. Let's look at some ways in which embedded LiveCode scripting can be useful.
Date and time. A common desire is to display the current date on the web page. This is easily done with LiveCode. (Keep in mind that since .lc scripts are run on the server, the date and time reported will be the settings on the server, not the client. Our local LiveCode server , hummac, is located in Provo, Utah, USA.)
<p>Today's date is <?lc put the date ?>. </p>
Dynamic HTML lists and tables. Since you can use any LiveCode structure in .lc files, you can use, for example, repeat loops to create dynamic lists or tables. Note that we also build the HTML "framework" for the LiveCode output at the same time.
<?lc put the short date into tDate set the itemDelimiter to "/" put item 1 of tDate into tMonth put "<p>Months elapsed this year:</p>" put "<p>" repeat with x = 1 to tMonth put line x of the monthNames if x = tMonth then put " (current month)<br />" else put "<br />" end if end repeat put "</p>" ?>
Defining custom handlers in .lc files; Dynamic table creation. By creatively interspersing HTML tags with LiveCode <?lc .. ?> segments we can create sophisticated dynamic page elements. Here is the calendar example that we did in class. It was adapted slightly from the HTML Coding Exercise from another course. Remember that in .lc files, functions and handlers can be defined anywhere within the file, and can be called from anywhere in the file. In this way a .lc file can be thought of as similar to an object script in LiveCode.
<?lc function q pString return quote & pString & quote end q function makeCalendar pMonth,pStartDay,pEndDate put 1 into tDate put "<p><strong>" & pMonth & "</strong></p>" & return into tCal put "<table border=" & q("1") & ">" & return after tCal repeat with tRow = 1 to 6 if tRow = 6 and tDate > pEndDate then # don't make a sixth row if no dates left in month exit repeat end if put "<tr align=" & q("right") & ">" & return after tCal repeat with tCol = 1 to 7 if (tRow = 1 and tCol < pStartDay) OR (tDate > pEndDate) then put " " into tContents else put tDate into tContents add 1 to tDate end if put "<td>" & tContents & "</td>" after tCal end repeat put return & "</tr>" after tCal end repeat put return & "</table>" after tCal return tCal end makeCalendar put the long date into tDate put "<p>Today's date is " & tDate & ".</p>" put word 1 of item 2 of tDate into tMonth convert tDate to dateitems subtract (item 3 of tDate - 1) from item 3 of tDate convert tDate to dateitems put item 7 of tDate into tStartDay add 1 to item 2 of tDate convert tDate to dateitems subtract 1 from item 3 of tDate convert tDate to dateitems put makeCalendar(tMonth,tStartDay,item 3 of tDate) ?>
You can see the output of this file at http://dight310.byu.edu/students/asay/beginning.lc.