Lua Pages
A Lua Page is a text template file which will be processed by CGILua before the HTTP server sends it to the client. CGILua does not process the text itself but look for some special markups that include Lua code into the file. After all those markups are processed and merged with the template file, the results are sent to the client.
Lua Pages have a default .lp extension. They are a simpler way to make a dynamic page because there is no need to send the HTTP headers. Usually Lua Pages are HTML pages so CGILua sends the HTML header automatically.
Since there are some restrictions on the uses of HTTP headers sometimes a Lua Script will have to be used instead of a Lua Page.
The fundamental Lua Page markups are:
<?lua chunk ?>
Processes and merges the Lua chunk execution results where the markup is located in the template. The alternative form <% chunk %> can also be used.
<?lua= expression ?>
Processes and merges the Lua expression evaluation where the markup is located in the template. The alternative form <%= expression %> can also be used.
Note that the ending mark could not appear inside a Lua chunk or Lua expression even inside quotes. The Lua Pages pre-processor just makes global substitutions on the template, searching for a matching pair of markups and generating the corresponding Lua code to achieve the same result as the equivalent Lua Script.
The second example on the previous section could be written using a Lua Page like:
<html>
<?lua
if cgilua.QUERY.language == 'english' then
greeting = 'Hello World!'
elseif cgilua.QUERY.language == 'portuguese' then
greeting = 'Olá Mundo!'
else
greeting = '[unknown language]'
end
?>
<head>
<title><%= greeting %></title>
</head>
<body>
<strong><%= greeting %></strong>
</body>
</html>
HTML tags and Lua Page tags can be freely intermixed. However, as on other template languages, it's considered a best practice to not use explicit Lua logic on templates. The recommended aproach is to use only function calls that returns content chunks, so in this example, assuming that function getGreeting was definied in file functions.lua as follows:
function getGreeting()
local greeting
if cgilua.QUERY.language == 'english' then
greeting = 'Hello World!'
elseif cgilua.QUERY.language == 'portuguese' then
greeting = 'Olá Mundo!'
else
greeting = '[unknown language]'
end
return greeting
end
the Lua Page could be rewriten as:
<?lua
assert (loadfile"functions.lua")()
?>
<html>
<head>
<title><%= getGreeting() %></title>
</head>
<body>
<strong><%= getGreeting() %></strong>
</body>
</html>
Another interesting feature of Lua Pages is the intermixing of Lua and HTML. It is very usual to have a list of values in a table, iterate over the list and show the items on the page.
A Lua Script could do that using a loop like:
cgilua.put("<ul>")
for i, item in ipairs(list) do
cgilua.put("<li>"..item.."</li>")
end
cgilua.put("</ul>")
The equivalent loop in Lua Page would be:
<ul>
<% for i, item in ipairs(list) do %>
<li><%= item %></li>
<% end %>
</ul>