View Source Config (Elixir v1.12.2)
A simple keyword-based configuration API.
Example
This module is most commonly used to define application configuration,
typically in config/config.exs:
import Config
config :some_app,
key1: "value1",
key2: "value2"
import_config "#{config_env()}.exs"import Config will import the functions config/2, config/3
config_env/0, config_target/0, and import_config/1
to help you manage your configuration.
config/2 and config/3 are used to define key-value configuration
for a given application. Once Mix starts, it will automatically
evaluate the configuration file and persist the configuration above
into :some_app's application environment, which can be accessed in
as follows:
"value1" = Application.fetch_env!(:some_app, :key1)Finally, the line import_config "#{config_env()}.exs" will import
other config files based on the current configuration environment,
such as config/dev.exs and config/test.exs.
Config also provides a low-level API for evaluating and reading
configuration, under the Config.Reader module.
Important: if you are writing a library to be used by other developers,
it is generally recommended to avoid the application environment, as the
application environment is effectively a global storage. Also note that
the config/config.exs of a library is not evaluated when the library is
used as a dependency, as configuration is always meant to configure the
current project. For more information, read our library guidelines.
Migrating from use Mix.Config
The Config module in Elixir was introduced in v1.9 as a replacement to
Mix.Config, which was specific to Mix and has been deprecated.
You can leverage Config instead of Mix.Config in three steps. The first
step is to replace use Mix.Config at the top of your config files by
import Config.
The second is to make sure your import_config/1 calls do not have a
wildcard character. If so, you need to perform the wildcard lookup
manually. For example, if you did:
import_config "../apps/*/config/config.exs"It has to be replaced by:
for config <- "../apps/*/config/config.exs" |> Path.expand(__DIR__) |> Path.wildcard() do
import_config config
endThe last step is to replace all Mix.env() calls by config_env().
config/runtime.exs
For runtime configuration, you can use the config/runtime.exs file.
It is executed right before applications start in both Mix and releases
(assembled with mix release).
Link to this section Summary
Functions
Configures the given root_key.
Configures the given key for the given root_key.
Returns the environment this configuration file is executed on.
Returns the target this configuration file is executed on.
Imports configuration from the given file.
Link to this section Functions
Configures the given root_key.
Keyword lists are always deep-merged.
Examples
The given opts are merged into the existing configuration
for the given root_key. Conflicting keys are overridden by the
ones specified in opts. For example, the application
configuration below
config :logger,
level: :warn,
backends: [:console]
config :logger,
level: :info,
truncate: 1024will have a final configuration for :logger of:
[level: :info, backends: [:console], truncate: 1024]Configures the given key for the given root_key.
Keyword lists are always deep merged.
Examples
The given opts are merged into the existing values for key
in the given root_key. Conflicting keys are overridden by the
ones specified in opts. For example, the application
configuration below
config :ecto, Repo,
log_level: :warn,
adapter: Ecto.Adapters.Postgres
config :ecto, Repo,
log_level: :info,
pool_size: 10will have a final value of the configuration for the Repo
key in the :ecto application of:
[log_level: :info, pool_size: 10, adapter: Ecto.Adapters.Postgres]Returns the environment this configuration file is executed on.
In Mix projects this function returns the environment this configuration
file is executed on. In releases, the environment when mix release ran.
This is most often used to execute conditional code:
if config_env() == :prod do
config :my_app, :debug, false
endReturns the target this configuration file is executed on.
This is most often used to execute conditional code:
if config_target() == :host do
config :my_app, :debug, false
endImports configuration from the given file.
In case the file doesn't exist, an error is raised.
If file is a relative, it will be expanded relatively to the directory the current configuration file is in.
Examples
This is often used to emulate configuration across environments:
import_config "#{config_env()}.exs"Note, however, some configuration files, such as config/runtime.exs
does not support imports, as they are meant to be copied across
systems.