More Options  

More Options is a library for defining configuration options in Rust. Options can be initialized in code, bound from configuration, and/or composed through dependency injection (DI).

You may be looking for:

• User Guide
• API Documentation
• Release Notes

Features

This crate provides the following features:

• default - Abstractions for options
• async - Enable options in asynchronous contexts
• di - Dependency injection extensions
• cfg - Dependency injection extensions to bind configurations to options

Options Pattern

The options pattern uses structures to provide strongly typed access to groups of related settings without having to know how the settings were configured. The settings can be set explicitly in code or they can come from an external configuration source such as a file.

Consider the following options:

pub struct EndpointOptions {
    pub url: String,
    pub retries: usize,
}

These might be used by a HTTP client as follows:

use options::Options;
use std::rc::Rc;

pub struct HttpClient {
    options: Rc<dyn Options<EndpointOptions>>,
}

impl HttpClient {
    pub fn new(options: Rc<dyn Options<EndpointOptions>>) -> Self {
        Self { options }
    }

    pub fn retries(&self) -> usize {
        self.options.value().retries
    }
}

Options in Action

The defined options can be used in any number of ways, including just explicitly specifying the settings.

use crate::*;
use std::rc::Rc;

fn main() {
    let options = Rc::new(options::create(EndpointOptions {
        url: "https://tempuri.org",
        retries: 2,
    }));
    let client = HttpClient::new(options);
    // TODO: use the client
}

If you expect to process your options from an external data source, then you'll almost certainly require supporting deserialization using serde as follows:

use serde::Deserialize;

#[derive(Deserialize)]
pub struct EndpointOptions {
    pub url: String,
    pub retries: usize,
}

Suppose you had the following appSettings.json file:

{
  "url": "https://tempuri.org",
  "retries": 3
}

You can construct the options from the settings by including the more-config crate as follows:

use crate::*;
use config::{*, ext::*};

fn main() {
    let config = DefaultConfigurationBuilder::new()
        .add_json_file("appsettings.json")
        .build()
        .unwrap();
    let options: EndpointOptions = config.reify();
    let client = HttpClient::new(options);
    // TODO: use the client
}

You can go one step further and combine that configuration with the more-di crate to assemble all of the pieces for you:

use crate::*;
use config::{*, ext::*};
use di::*;
use std::rc::Rc;

fn main() {
    let config = Rc::from(
        DefaultConfigurationBuilder::new()
            .add_json_file("appsettings.json")
            .build()
            .unwrap()
            .as_config());
    let provider = ServiceCollection::new()
        .add(transient_as_self::<HttpClient>())
        .apply_config::<EndpointOptions>(config)
        .build_provider()
        .unwrap();
    let client = provider.get_required::<HttpClient>();
    // TODO: use the client
}

License

This project is licensed under the MIT license.