Mix v1.1.1 Mix.Config

Module for defining, reading and merging app configurations.

Most commonly, this module is used to define your own configuration:

use Mix.Config

config :plug,
  key1: "value1",
  key2: "value2"

import_config "#{Mix.env}.exs"

All config/* macros, including import_config/1, are used to help define such configuration files.

Furthermore, this module provides functions like read!/1, merge/2 and friends which help manipulate configurations in general.

Configuration set using Mix.Config will set the application env, so that Application.get_env/3 and other Application functions can be used at run or compile time to retrieve or change the configuration.

For example, the :key1 value from application :plug (see above) can be retrieved with:

"value1" = Application.fetch!(:plug, :key1)

Summary

Functions

merge(config1, config2)

Merges two configurations

persist(config)

Persists the given configuration by modifying the configured applications environment

read!(file)

Reads and validates a configuration file

read_wildcard!(path)

Reads many configuration files given by wildcard into a single config. Raises an error if path is a concrete filename (with no wildcards) but the corresponding file does not exist

validate!(config)

Validates a configuration

Macros

config(app, opts)

Configures the given application

config(app, key, opts)

Configures the given key for the given application

import_config(file)

Imports configuration from the given file

Functions

merge(config1, config2)

Merges two configurations.

The configuration of each application is merged together with the values in the second one having higher preference than the first in case of conflicts.

Examples

iex> Mix.Config.merge([app: [k: :v1]], [app: [k: :v2]])
[app: [k: :v2]]

iex> Mix.Config.merge([app1: []], [app2: []])
[app1: [], app2: []]

persist(config)

Persists the given configuration by modifying the configured applications environment.

Returns the configured apps.

read!(file)

Reads and validates a configuration file.

read_wildcard!(path)

Reads many configuration files given by wildcard into a single config. Raises an error if path is a concrete filename (with no wildcards) but the corresponding file does not exist.

validate!(config)

Validates a configuration.

Macros

config(app, opts)

Configures the given application.

Keyword lists are always deep merged.

Examples

The given opts are merged into the existing configuration for the given app. Conflicting keys are overridden by the ones specified in opts. For example, the declaration below:

config :lager,
  log_level: :warn,
  mode: :truncate

config :lager,
  log_level: :info,
  threshold: 1024

Will have a final configuration of:

[log_level: :info, mode: :truncate, threshold: 1024]

This final configuration can be retrieved at run or compile time:

Application.get_all_env(:lager)

config(app, key, opts)

Configures the given key for the given application.

Keyword lists are always deep merged.

Examples

The given opts are merged into the existing values for key in the given app. Conflicting keys are overridden by the ones specified in opts. For example, the declaration below:

config :ecto, Repo,
  log_level: :warn

config :ecto, Repo,
  log_level: :info,
  pool_size: 10

Will have a final value for Repo of:

[log_level: :info, pool_size: 10]

This final value can be retrieved at run or compile time:

Application.get_env(:ecto, Repo)

import_config(file)

Imports configuration from the given file.

The path is expected to be relative to the directory the current configuration file is on.

Examples

This is often used to emulate configuration across environments:

import_config "#{Mix.env}.exs"

Or to import files from children in umbrella projects:

import_config "../apps/*/config/config.exs"