Crate envconf

Source
Expand description

Boilerplate free initialization of structs from environment variables

Usage example: It is usual that programs rely on environment variables to define their behavior, especially for cloud and microservies applications. Imagine you need to setup a database connection by reading the following environment variables:

  • DB_HOST
  • DB_PORT
  • DB_USER
  • DB_PASSWORD
  • DB_NAME

With this library crate, it is as easy as this:

use envconf::{Setting, Error};

#[derive(Setting)]
struct DBSettings {
    #[conf(env = "DB_HOST", default = "localhost")]
    host: String,
    #[conf(env = "DB_PORT", default = 5432)]
    port: usize,
    #[conf(default = "myuser")]  // hardcoded setting
    user: String,
    #[conf(env = "DB_PASSWORD")] // env variable required
    password: String,
    #[conf(env = "DB_NAME", default = "mydb")]
    name: String,
}

fn main() -> Result<(), Error<'static>> {
    // This env is mandatory, so it needs to be set!
    std::env::set_var("DB_PASSWORD", "secret");

    // Initialize config from environment variables
    // Read the crate docs to check the possible Error variants
    let db_settings = DBSettings::init()?;

    assert_eq!(db_settings.host, "localhost");
    assert_eq!(db_settings.port, 5432);
    assert_eq!(db_settings.user, "myuser");
    assert_eq!(db_settings.password, "secret");
    assert_eq!(db_settings.name, "mydb");

    Ok(())
}

Enums§

  • Error
    Possible errors returned by the init method

Traits§

Derive Macros§