An OTP application for compiling configuration values into well-structured and validated namespaces.
Configuration values can be loaded via an implementation of the ecc_gen_driver behavior
module. By default, a driver is supplied for loading configuration values via environment variables and an optional
dotenv file path. This driver can be found in the ecc_env_driver module.
Validation and namespacing of configuration values occurs through modules that implement
the ecc_gen_config behavior module. Each configuration module exports a set of functions
that:
- declare the namespace its configuration will be stored under (this must be unique), via
namespace/0 - transform the configuration set (loaded by a
ecc_gen_drivermodule) into a validated structure, viaload/1 - provide a means to access attributes of this validated structure, via
get/2
An example implementation of ecc_gen_config can be found in the test suite,
under ecc_test_config.erl.
$ rebar3 compile
$ rebar3 eunit
$ rebar3 edoc
$ rebar3 fmt
Example configuration module implementation:
-module(example_config_module).
-behavior(ecc_gen_config).
-export([namespace/0, load/1, get/2]).
-record(example_config_rec, {
foo :: string(),
bar :: integer(),
baz :: boolean()
}).
%%%===================================================================
%%% ecc_gen_config callbacks
%%%===================================================================
namespace() ->
?MODULE.
load(Maps = #{"FOO" := Foo, "BAR" := Bar}) ->
% or handle this as a result, for simplicity of this example we won't provide a helpful error message
BarInt = parse_int(Bar),
% or handle this as a result, for simplicity of this example we won't provide a helpful error message
BazBool = parse_bool(maps:get("BAZ", Maps, "false")),
{ok, #example_config_rec{foo = Foo, bar = BarInt, baz = BazBool}};
load(#{"FOO" := _Foo}) ->
{error, "missing required FOO value"};
load(#{"BAR" := _Bar}) ->
{error, "missing required BAR value"};
load(_) ->
{error, "missing required FOO and BAR values"}.
get(foo, #example_config_rec{foo = Foo}) ->
Foo;
get(bar, #example_config_rec{bar = Bar}) ->
Bar;
get(baz, #example_config_rec{baz = Baz}) ->
Baz;
get(_, _) ->
undefined.
%%%===================================================================
%%% Internal functions
%%%===================================================================
parse_int(Val) when is_list(Val) ->
erlang:list_to_integer(Val).
parse_bool("true") ->
true;
parse_bool("false") ->
false.Then to register this module with the ecc application:
ok = ecc:register(example_config_module)Subsequent usage, once the configuration module has been registered:
#example_config_rec{foo = Foo} = ecc:namespace(example_config_module),
Foo = ecc:key(example_config_module, foo)
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