Trait EnvSource 

pub trait EnvSource {
    // Required method
    fn var(&self, key: &str) -> Option<String>;

    // Provided method
    fn var_any(&self, keys: &[&str]) -> Option<String> { ... }
}

A read-only view of environment variables.

Implemented by SystemEnv (the real process environment) in production and by an in-memory map in tests, so env-parsing boundaries can be tested without mutating the process-global environment.

Required Methods

fn var(&self, key: &str) -> Option<String>

Returns the value of key, or None if it is unset (or, for the process environment, not valid Unicode).

Provided Methods

fn var_any(&self, keys: &[&str]) -> Option<String>

Returns the first set value among keys, in order.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<T: EnvSource + ?Sized> EnvSource for &T

&T is an EnvSource whenever T is, so callers can pass &SystemEnv or &map_env to functions taking &impl EnvSource without ceremony.

fn var(&self, key: &str) -> Option<String>

Implementors

impl EnvSource for SettingsEnv

impl EnvSource for SystemEnv