In config.exs, use a string, a function or a tuple:

config :ipay88, backend_url: System.get_env("IPAY88_BACKEND_URL")

or:

config :ipay88, backend_url: {:system, "IPAY88_BACKEND_URL"}

or:

config :ipay88, backend_url: {MyApp.Config, :ipay88_backend_url, []}

Specs

json_library() :: module()

In config.exs your implicit or expicit configuration is:

config :ipay88, json_library: Poison # defaults to Jason but can be configured to Poison

In config.exs, use a string, a function or a tuple:

config :ipay88, merchant_code: System.get_env("IPAY88_MERCHANT_CODE")

or:

config :ipay88, merchant_code: {:system, "IPAY88_MERCHANT_CODE"}

or:

config :ipay88, merchant_code: {MyApp.Config, :ipay88_merchant_code, []}

In config.exs, use a string, a function or a tuple:

config :ipay88, merchant_key: System.get_env("IPAY88_MERCHANT_KEY")

or:

config :ipay88, merchant_key: {:system, "IPAY88_MERCHANT_KEY"}

or:

config :ipay88, merchant_key: {MyApp.Config, :ipay88_merchant_key, []}

Specs

resolve(atom(), any()) :: any()

Resolves the given key from the application's configuration returning the wrapped expanded value. If the value was a function it get's evaluated, if the value is a touple of three elements it gets applied.

In config.exs, use a string, a function or a tuple:

config :ipay88, response_url: System.get_env("IPAY88_RESPONSE_URL")

or:

config :ipay88, response_url: {:system, "IPAY88_RESPONSE_URL"}

or:

config :ipay88, response_url: {MyApp.Config, :ipay88_response_url, []}