基本示例

extern crate preferences;
use preferences::{AppInfo, PreferencesMap, Preferences};

const APP_INFO: AppInfo = AppInfo{name: "preferences", author: "Rust language community"};

fn main() {

    // Create a new preferences key-value map
    // (Under the hood: HashMap<String, String>)
    let mut faves: PreferencesMap<String> = PreferencesMap::new();

    // Edit the preferences (std::collections::HashMap)
    faves.insert("color".into(), "blue".into());
    faves.insert("programming language".into(), "Rust".into());

    // Store the user's preferences
    let prefs_key = "tests/docs/basic-example";
    let save_result = faves.save(&APP_INFO, prefs_key);
    assert!(save_result.is_ok());

    // ... Then do some stuff ...

    // Retrieve the user's preferences
    let load_result = PreferencesMap::<String>::load(&APP_INFO, prefs_key);
    assert!(load_result.is_ok());
    assert_eq!(load_result.unwrap(), faves);

}

使用自定义数据类型

extern crate preferences;
extern crate serde;
use preferences::{AppInfo, Preferences};
use serde::{Serialize, Deserialize};

const APP_INFO: AppInfo = AppInfo{name: "preferences", author: "Rust language community"};

// Deriving `Serialize` and `Deserialize` on a struct/enum automatically implements
// the `Preferences` trait.
#[derive(Serialize, Deserialize, PartialEq, Debug)]
struct PlayerData {
    level: u32,
    health: f32,
}

fn main() {

    let player = PlayerData{level: 2, health: 0.75};

    let prefs_key = "tests/docs/custom-types";
    let save_result = player.save(&APP_INFO, prefs_key);
    assert!(save_result.is_ok());

    // Method `load` is from trait `Preferences`.
    let load_result = PlayerData::load(&APP_INFO, prefs_key);
    assert!(load_result.is_ok());
    assert_eq!(load_result.unwrap(), player);

}

使用自定义数据类型与 PreferencesMap 一起使用

extern crate preferences;
extern crate serde;
use preferences::{AppInfo, PreferencesMap, Preferences};
use serde::{Serialize, Deserialize};

const APP_INFO: AppInfo = AppInfo{name: "preferences", author: "Rust language community"};

#[derive(Serialize, Deserialize, PartialEq, Debug)]
struct Point(f32, f32);

fn main() {

    let mut places = PreferencesMap::new();
    places.insert("treasure".into(), Point(1.0, 1.0));
    places.insert("home".into(), Point(-1.0, 6.6));

    let prefs_key = "tests/docs/custom-types-with-preferences-map";
    let save_result = places.save(&APP_INFO, prefs_key);
    assert!(save_result.is_ok());

    let load_result = PreferencesMap::load(&APP_INFO, prefs_key);
    assert!(load_result.is_ok());
    assert_eq!(load_result.unwrap(), places);

}

使用自定义数据类型与可序列化容器一起使用

extern crate preferences;
extern crate serde;
use preferences::{AppInfo, Preferences};
use serde::{Serialize, Deserialize};

const APP_INFO: AppInfo = AppInfo{name: "preferences", author: "Rust language community"};

#[derive(Serialize, Deserialize, PartialEq, Debug)]
struct Point(usize, usize);

fn main() {

    let square = vec![
        Point(0,0),
        Point(1,0),
        Point(1,1),
        Point(0,1),
    ];

    let prefs_key = "tests/docs/custom-types-in-containers";
    let save_result = square.save(&APP_INFO, prefs_key);
    assert!(save_result.is_ok());

    let load_result = Vec::<Point>::load(&APP_INFO, prefs_key);
    assert!(load_result.is_ok());
    assert_eq!(load_result.unwrap(), square);

}

内部机制

数据被写入活动用户主目录下的平面文件，该位置由操作系统特定。此位置由 app_dirs 框架和数据类型 UserConfig 决定。在数据目录内，文件存储在一个文件夹层次结构中，该层次结构与传递给 save(..) 的偏好键的清理版本相对应。

数据以JSON格式存储。这有几个优点

• 人类可读且自描述
• 比例如XML更紧凑
• 比例如TOML有更高的采用率和语言兼容性
• 不依赖于如二进制等一致的内存布局

当然，你可以自己实现 Preferences 并将你的用户数据存储在任何位置和格式中。但这将违背这个库的目的。😊