Show information on web-page from external process in n2o framework

Question

How can I show information from external processes in N2O framefork.

Code like this:

tokyoWeather() ->
     timer:sleep(10000),
     Data = getTokyoWeater(),
     ??? SHOW_ON_PAGES,
     tokyoWeather().
lisbonWeather() ->
     timer:sleep(10000),
     Data = getLisbonWeater(),
     ??? SHOW_ON_PAGES,
     lisbonWeather().

Page1:

body() ->
    [ #panel { id=TokyoWeather text= <<>> },
      #panel { id=LisbonWeather, text= <<>> },
      ...].

Page2:

body() ->
    [ #panel { id=TokyoWeather text= <<>> },
      #panel { id=LisbonWeather, text= <<>> },
      ...].

Thanks in advance.

m2k · Answer 1 · 2015-02-08T19:09:09.893

2

Use wf:reg and wf:flush functions. Example: /samples/apps/review/src/index.erl

Register unique name for a page-process:

23: event(init) -> wf:reg(room)...
Updating DOM:

60: wf:insert_bottom(history, Terms)
Flushing changes to browser using page-process name:

62: wf:flush(room)

edited Feb 08 '15 at 19:09

answered May 26 '14 at 11:03

m2k

21
5

score 1 · Answer 2 · answered Oct 30 '16 at 21:31

Documentation suggests using wf:reg/1 and wf:flush. However, this requires you to register process into a pool, which is handy for when you want to manipulate multiple processes at once, but quite redundant otherwise.

Another interesting function the N2O book mentions is wf:flush/1. Its description claims that it does something completely different from wf:flush/0, while in reality it does not. It really just collects the wf actions placed into a "buffer" and sends them via wf:send/2 to a registered supposedly websocket processes. Meanwhile the websocket process sits in a timed receive loop.

After some N2O's code inspection, there is a pretty simple solution, in my opinion:

Starting at process that can render actions(e.g. the websocket process), spawn your desired function and pass the parent process id as one of its parameters
```
async_render() ->
  Pid = self(),
  spawn(fun() -> update(Pid) end).
```
Perform your wf actions in now asynchronous function, then retrieve the queued actions, clear the buffer, and finally send the a tuple of {flush, Actions} to your parent process.
```
update(Pid) ->
  %% Your wf:insert..., update, etc. code here
  Actions = wf:actions(),
  wf:actions([]),
  Pid ! {flush, Actions}.
```

The rest is done by N2O for you :)

Show information on web-page from external process in n2o framework

2 Answers2