A Rust library for modifying structs via environment variables.

Unlike envy, this does not create a new object. It is used to reconfigure an existing structure (after having parsed it from a config file, for example).

Ignored fields

If a certain field should not be configurable via environment variables, mark it with #[env(ignore)].

Examples

Creating a config structure:

``` use derive_environment::FromEnv;

[derive(Default, FromEnv)]

pub struct Config { // ... }

// Creates a base configuration struct to add on to. // Normally this would be created using serde from a config file. let mut config = Config::default(); // Names the struct "MYCONFIG", which acts as a prefix. config.withenv("MY_CONFIG").unwrap(); ```

Nesting fields:

``` use derive_environment::FromEnv;

[derive(FromEnv)]

struct ServerConfig { port: u16, }

[derive(FromEnv)]

pub struct Config { server: ServerConfig, } ```

Generates: - MYCONFIGSERVER_PORT

Vector of Nested fields:

``` use derive_environment::FromEnv;

// Vec's FromEnv implementation requires Default.

[derive(Default, FromEnv)]

struct ServerConfig { port: u16, }

[derive(FromEnv)]

pub struct Config { servers: Vec, } ```

Generates: - MYCONFIGSERVER0PORT