Struct Environment

pub struct Environment { /* private fields */ }

An environment source collects a dictionary of environment variables values into a hierarchical config Value type. We have to be aware how the config tree is created from the environment dictionary, therefore we are mindful about prefixes for the environment keys, level separators, encoding form (kebab, snake case) etc.

Implementations

impl Environment

pub fn with_prefix(s: &str) -> Self

Optional prefix that will limit access to the environment to only keys that begin with the defined prefix.

A prefix with a separator of _ is tested to be present on each key before its considered to be part of the source environment.

For example, the key CONFIG_DEBUG would become DEBUG with a prefix of config.

pub fn prefix(self, s: &str) -> Self

See Environment::with_prefix

pub fn prefix_separator(self, s: &str) -> Self

Optional character sequence that separates the prefix from the rest of the key

pub fn separator(self, s: &str) -> Self

Optional character sequence that separates each key segment in an environment key pattern. Consider a nested configuration such as redis.password, a separator of _ would allow an environment key of REDIS_PASSWORD to match.

pub fn list_separator(self, s: &str) -> Self

When set and try_parsing is true, then all environment variables will be parsed as Vec<String> instead of String. See with_list_parse_key when you want to use Vec<String> in combination with String.

pub fn with_list_parse_key(self, key: &str) -> Self

Add a key which should be parsed as a list when collecting Values from the environment. Once list_separator is set, the type for string is Vec<String>. To switch the default type back to type Strings you need to provide the keys which should be Vec<String> using this function.

pub fn ignore_empty(self, ignore: bool) -> Self

Ignore empty env values (treat as unset).

pub fn try_parsing(self, try_parsing: bool) -> Self

Note: enabling try_parsing can reduce performance it will try and parse each environment variable 3 times (bool, i64, f64)

pub fn keep_prefix(self, keep: bool) -> Self

pub fn source(self, source: Option<Map<String, String>>) -> Self

Alternate source for the environment. This can be used when you want to test your own code using this source, without the need to change the actual system environment variables.

Example

#[test]
fn test_config() -> Result<(), config::ConfigError> {
  #[derive(Clone, Debug, Deserialize)]
  struct MyConfig {
    pub my_string: String,
  }

  let source = Environment::default()
    .source(Some({
      let mut env = HashMap::new();
      env.insert("MY_STRING".into(), "my-value".into());
      env
  }));

  let config: MyConfig = Config::builder()
    .add_source(source)
    .build()?
    .try_into()?;
  assert_eq!(config.my_string, "my-value");

  Ok(())
}

Trait Implementations

impl Clone for Environment

fn clone(&self) -> Environment

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Environment

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Environment

fn default() -> Environment

Returns the “default value” for a type.

impl Source for Environment

fn clone_into_box(&self) -> Box<dyn Source + Send + Sync>

fn collect(&self) -> Result<Map<String, Value>, ConfigError>

Collect all configuration properties available from this source and return a Map.

fn collect_to(&self, cache: &mut Value) -> Result<(), ConfigError>

Collects all configuration properties to a provided cache.