serdesingleor_vec

This crate provides the SingleOrVec Type which allows parsing either a single type T or a vector of type T using serde. This is required when a server either returns an array if there are multiple values or one value if there is only one.

Example

```rust

[derive(Deserialize, Serialize)]

struct Response { single: SingleOrVec<'static, u8>, multiple: SingleOrVec<'static, u8>, }

let json = r#"{ "single": 0, "multiple": [ 0, 1, 2 ] }"#; let res: Response = serdejson::fromstr(json).unwrap(); asserteq!(json, &serdejson::tostringpretty(&res).unwrap()); ```

Format

By default the SingleOrVec Type deserializes its content either to a single value or an array if it contains multiple values. To change this behaviour, its possible to define the output format.

```rust

[derive(Deserialize, Serialize)]

struct Response { single: SingleOrVec<'static, u8>, multiple: SingleOrVec<'static, u8>, }

let json = "[0]";

let res: SingleOrVec<', u8, PreferSingle> = serdejson::fromstr(json).unwrap(); asserteq!("0", &serdejson::tostring(&res).unwrap());

let res: SingleOrVec<', u8, AlwaysVector> = serdejson::fromstr(json).unwrap(); asserteq!("[0]", &serdejson::tostring(&res).unwrap()); ```

Storage Backend

The default Backend is a Vec<T> and thus always results in an allocation. An alternativ is to use a Cow<'_, T> as backend which only requires an allocation for a single value.

Note that this is only valid when using or serializing this value, deserialisation always allocates due to serde#1852

rust let json = "[0,1,2]"; let res: SingleOrVec<'_, u8, PreferSingle, Cow<'_, [u8]>> = serde_json::from_str(json).unwrap(); assert_eq!(json, &serde_json::to_string(&res).unwrap());

Custom Storage Type

Its also possible to implement Custom Storage Backends by using the Storage Trait.

```rust use arrayvec::ArrayVec;

struct ArrayVecStorage {}

impl Storage<'_, T> for ArrayVecStorage { type Backing = ArrayVec<[T; 4]>;

fn single(ty: T) -> Self::Backing {
    let mut vec = ArrayVec::new();
    vec.push(ty);
    vec
}

fn get_first_with_len(b: &Self::Backing) -> Option<(&T, usize)> {
    b.split_first().map(|(t, r)| (t, r.len()))
}

}

let json = "[0,1,2]"; let res: SingleOrVec<', u8, PreferSingle, ArrayVecStorage> = serdejson::fromstr(json).unwrap(); asserteq!(json, &serdejson::tostring(&res).unwrap());

let json = "0"; let res: SingleOrVec<', u8, PreferSingle, ArrayVecStorage> = serdejson::fromstr(json).unwrap(); asserteq!(json, &serdejson::tostring(&res).unwrap()); ```

no_std

It is possible to use this crate with no_std, however, like serde, either std or alloc is required.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

License: MIT OR Apache-2.0