Serialize struct with one field as inner field

[D-Konopka]

I've got a struct with one field.
How i can serialize it as the inner field without the extra wrapper.

For example how i can make ExampleStruct serialize as Vec<u64>.

• This: [1, 2, 3]
• Not this { "vec": [1, 2, 3] }

use serde::Serialize;

#[derive(Debug, Serialize)]
struct ExampleStruct{
    vec: Vec<u64>
}

fn main() {
    let example = ExampleStruct { vec: vec![1,2,3] };
    println!("{:?}", serde_json::to_string(&example));
}

[jofas]

I think the easiest solution in your case would be to just make ExampleStruct a tuple struct instead of a struct with named fields.

use serde::Serialize;

#[derive(Debug, Serialize)]
struct ExampleStruct(Vec<u64>);

fn main() {
    let example = ExampleStruct(vec![1,2,3]);
    println!("{}", serde_json::to_string(&example).unwrap());
}

Playground.

[steffahn]

Note that transparent treatment of newtype-style structs is just an implementation choice of serde_json; the field is still wrapped with serialize_newtype_struct, which merely encourages serializers to consider treating it fully transparently.

To hide the layer completely from serializers, it’s also possible to use #[serde(transparent)] instead. This is also compatible with named fields.

[jofas]

Ah yes, forgot about serde(transparent). I was looking into making serde(flatten) work on the inner field, but it doesn't work with collections. My other thought was serde(untagged), but that obviously only applies to enums.