Trait figment::providers::Format

source · [−]
pub trait Format: Sized {
    type Error: Error;

    const NAME: &'static str;

    fn from_str<'de, T: DeserializeOwned>(
        string: &'de str
    ) -> Result<T, Self::Error>;

    fn from_path<T: DeserializeOwned>(path: &Path) -> Result<T, Self::Error> { ... }
    fn file<P: AsRef<Path>>(path: P) -> Data<Self> { ... }
    fn string(string: &str) -> Data<Self> { ... }
}
Expand description

Trait implementable by text-based Data format providers.

Instead of implementing Provider directly, types that refer to data formats, such as Json and Toml, implement this trait. By implementing Format, they become Providers indirectly via the Data type, which serves as a provider for all T: Format.

use figment::providers::Format;

// If `T` implements `Format`, `T` is a `Provider`.
// Initialize it with `T::file()` or `T::string()`.
let provider = T::file("foo.fmt");
let provider = T::string("some -- format");

Implementing

There are two primary implementation items:

  1. Format::NAME: This should be the name of the data format: "JSON" or "TOML". The string is used in the [metadata for Data].

  2. Format::from_str(): This is the core string deserialization method. A typical implementation will simply call an existing method like toml::from_str. For writing a custom data format, see serde’s writing a data format guide.

The default implementations for Format::from_path(), Format::file(), and Format::string() methods should likely not be overwritten.

Required Associated Types

The data format’s error type.

Required Associated Constants

The name of the data format, for instance "JSON" or "TOML".

Required Methods

Parses string as the data format Self as a T or returns an error if the string is an invalid T.

Provided Methods

Parses the file at path as the data format Self as a T or returns an error if the string is an invalid T. The default implementation calls Format::from_str() with the contents of the file.

Returns a Data provider that sources its values by parsing the file at path as format Self. See Data::file() for more details. The default implementation calls Data::file(path).

Returns a Data provider that sources its values by parsing string as format Self. See Data::string() for more details. The default implementation calls Data::string(string).

Implementors