Nitrogen, an Erlang web application library/framework Part 2

Slide 17

Why are we backslash escaping the underscore? Or is that backslash supposed to be a DOS directory separator? It will get removed by any Unix shell, so, at my peril, I'm going to omit it.

bash-4.1$ ./dev page my_page
Created page: ./site/src/my_page.erl
Remember to recompile!
bash-4.1$ emacs ../site/src/my_page.erl 
^Z
[1]+  Stopped                 emacs ../site/src/my_page.erl
bash-4.1$ bg
[1]+ emacs ../site/src/my_page.erl &
bash-4.1$ pwd
/home/sps/erlang-libs/nitrogen/rel/nitrogen/bin
bash-4.1$ ./dev compile
:: MAKE - site
Recompile: ./src/my_page
:: MAKE - ./site
 :: Done!

Seems to be working...

That's odd: tutorial says use port 8080 - how'd we switch from port 8000 to port 8080?

Browser says: Unable to connect. Let's try port 8000.

That worked.

Slide 19

Puzzling: "module:body()" seems to mean a module name is explicitly needed when interpolating(?) erlang "callouts", and "script" seems to imply that the script name is globally scoped within the browser (let's assume that erlang doesn't contain an internal javascript interpreter, ok?). Or is "script" supposed to also follow the "module:function(Args)" format, with the erlang result comprised of javascript code to be executed? Presumably this will be revealed...

Slide 20

Default template is what? "page:body()" doesn't occur in any version of site/src/my_page.erl nor site/src/index.erl. grep for it.

bash-4.1$ grep -Rl 'page:body()' ..
../site/templates/bare.html
../doc/org-mode/tutorial.html
../doc/org-mode/tutorial.org
../doc/html/tutorial.html

Ah, it must be ../site/templates/bare.html.

OK, that's me being dumb: site/templates/bare.html is explicitly referenced in index.erl and my_page.erl.

Doing the replacement suggested by the tutorial, without doing any compilation, removes all the page content, but provokes no error messages. Confirm by defining body1/0 in index.erl - which needs compilation. Interpolation confirmed.

"page" refers to the generic corresponding erlang module, e.g. "index.erl" or "my_page.erl" (for .../my/page). Any specific module:function can be referenced from within the template; an arbitrary expression causes a failure in "-convert_callback_tuple_to_function/4-fun-0-".

Slide 22

.
No surprises, although a <label> element normally occurs in a form, which isn't present here.

Slide 25

Again, where is the <form>?

Slide 26

A #panel is equivalent to a <div>.