Module zng::config

Config service, sources and other types.

The configuration service CONFIG separates config using from config writing. A config is a variable of a serializable type, widgets and other components request a config using an unique text name and then simply use the variable like any other. The app optionally sets one or more config sources that are automatically updated when a config variable changes and are monitored for changes that are propagated back to the config variables.

Sources

The default config source is the MemoryConfig that only lives for the app process lifetime, this can be used to connect different UI components, more importantly it also means that the CONFIG service always works so widgets can just set configs in case a persisting source is setup.

use zng::prelude::*;

fn txt_input() -> impl UiNode {
    TextInput!(CONFIG.get("example.txt", Txt::default))
}

fn txt_display() -> impl UiNode {
    Text!(CONFIG.get("example.txt", Txt::default))
}

Container! {
    child = txt_input();
    child_bottom = txt_display(), 20;
}

The example above uses a config "example.txt", the text will be wiped when the app is closed, but the app components are ready in case they are used in an app that enables persistent config.

The example below setups a JsonConfig that persists the configs to a JSON file. The file updates when a config variable is modified and the variables are updated when the file is modified externally.

let cfg = zng::config::JsonConfig::sync("target/tmp/example.config.json");
CONFIG.load(cfg);

Other Sources

The JSON format is available by default, TOML, YAML and RON are also available behind a feature flags, you can also implement your own source.

Apart from config sources that represents a format some meta sources are provided, they enables composite sources, such as having two sources app default and user where the user config file only records the non-default values.

The crate example examples/config.rs demonstrates a more complex setup:

use zng::config::*;

fn load_config() -> Box<dyn FallbackConfigReset> {
    // config file for the app, keys with prefix "main." are saved here.
    let user_cfg = JsonConfig::sync("target/tmp/example.config.json");
    // entries not found in `user_cfg` bind to this file first before going to embedded fallback.
    let default_cfg = ReadOnlyConfig::new(JsonConfig::sync("examples/res/config/defaults.json"));

    // the app settings.
    let main_cfg = FallbackConfig::new(user_cfg, default_cfg);

    // Clone a ref that can be used to reset specific entries.
    let main_ref = main_cfg.clone_boxed();

    // any other configs (Window::save_state for example)
    let other_cfg = JsonConfig::sync("target/tmp/example.config.other.json");

    CONFIG.load(SwitchConfig::new().with_prefix("main.", main_cfg).with_prefix("", other_cfg));

    main_ref
}

Full API

See zng_ext_config for the full config API.

Structs

• CONFIG
  Represents the app main config.
• FallbackConfig
  Represents a copy-on-write config source that wraps two other sources, a read-write config and a read-only fallback config.
• MemoryConfig
  Memory only config.
• RawConfigValue
  Represents any entry type in a config.
• ReadOnlyConfig
  Config wrapper that only provides read-only variables from the inner config.
• SwapConfig
  Represents a config source that can swap its backing config source without disconnecting any bound keys.
• SwitchConfig
  Represents multiple config sources that are matched by key.

Enums

• ConfigStatus
  Represents the current IO status of the config.

Traits

• AnyConfig
  Represents one or more config sources behind a dynamic reference.
• Config
  Represents one or more config sources.
• ConfigValue
  Marker trait for types that can stored in a Config.
• FallbackConfigReset
  Reset controls of a FallbackConfig.

Type Aliases

• ConfigKey
  Unique key to a config entry.
• JsonConfig
  Represents a config source that synchronizes with a JSON file.
• RonConfig
  Represents a config source that synchronizes with a RON file.
• TomlConfig
  Represents a config source that synchronizes with a TOML file.
• YamlConfig
  Represents a config source that synchronizes with a YAML file.