From Rails to Erlyweb - Part I

It's time to migrate our project from Rails to Erlyweb. I'll blog some tips of the procedure, focus on the differences between Rails and erlyweb.

1.How to handle params

Rails:

p = params.fetch(:p, 1)
s = params.fetch(:s, @@RECORDS_PER_PAGE)
p = p.to_i  
s = s.to_i  

Erlyweb:

-module(mymodel_controller)..
-define(RECORDS_PER_PAGE, "9").

list(A) ->
    P = yaws_params:get("p", A, "1"),
    S = yaws_params:get("s", A, ?RECORDS_PER_PAGE),
    Page = list_to_integer(P),
    Size = list_to_integer(S),
    ....

To get the above code working, I wrote a yaws_params.erl and placed under folder: apps\myapp\lib, maybe it should be part of Erlyweb?

-module(yaws_params).

-export([
   get/2,
   get/3
        ]).

get(Key, Arg) ->
    get(Key, Arg, undefined).

%% Usage: get(Key, Arg, Default)
get(Key, Arg, Default) ->
    Params = yaws_api:parse_query(Arg), %% in form of [{p, "2"}, {s, "1"}] etc.
    case lists:keysearch(Key, 1, Params) of
  false ->
      Default;
  {value, Tuple} ->
      Val = element(2, Tuple),
      if 
    Val == undefined -> Default;
    true -> Val
      end
    end.