CODEWITHSUNDEEP
configurationerlangerlang-otp
Nick Saw
Nick Saw

Reputation: 507

How to define config file variables?

I have a configuration file with:

{path, "/mnt/test/"}.
{name, "Joe"}.

The path and the name could be changed by a user. As I know, there is a way to save those variables in a module by usage of file:consult/1 in 

-define(VARIABLE, <parsing of the config file>).

Are there any better ways to read a config file when the module begins to work without making a parsing function in -define? (As I know, according to Erlang developers, it's not the best way to make a complicated functions in -define)

Upvotes: 3

Views: 924

Answers (1)

Eugen Dubrovin
Eugen Dubrovin

Reputation: 906

If you need to store config only when you start the application - you may use application config file which is defined in 'rebar.config'

{profiles, [
  {local,
    [{relx, [
      {dev_mode,      false},
      {include_erts,  true},
      {include_src,   false},
      {vm_args,       "config/local/vm.args"}]
      {sys_config,    "config/local/yourapplication.config"}]
     }]
  }
]}.

more info about this here: rebar3 configuration

next step to create yourapplication.config - store it in your application folder /app/config/local/yourapplication.config

this configuration should have structure like this example

[
    {
        yourapplicationname, [
            {path, "/mnt/test/"},
            {name, "Joe"}
        ]
    }
].

so when your application is started you can get the whole config data with 

{ok, "/mnt/test/"} = application:get_env(yourapplicationname, path)
{ok, "Joe"} = application:get_env(yourapplicationname, name)

and now you may -define this variables like:

-define(VARIABLE,
    case application:get_env(yourapplicationname, path) of
        {ok, Data} -> Data
        _   -> undefined
    end
).

Upvotes: 4

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