Wrapper types

Wrapper types make it easy to customize the way that fields of types are archived. They make it easier to adapt rkyv to existing data models, and make serializing and deserializing idiomatic for even complicated types.

Annotating a field with #[with(...)] will wrap that field with the given types when the struct is serialized or deserialized. There's no performance penalty to actually wrap types, but doing more or less work during serialization and deserialization can affect performance. This excerpt is from the documentation for ArchiveWith:

#[derive(Archive, Deserialize, Serialize)]
struct Example {
    a: i32,
    // Another i32 field, but not incremented this time
    b: i32,

The Incremented wrapper is wrapping a, and the definition causes that field to be incremented in its archived form.


The core type behind wrappers is With. This struct is transparent, meaning that it's like another name for the type inside of it. rkyv uses With to wrap your fields when serializing and deserializing, and when you write your own wrappers they will be used with With as well.

See ArchiveWith for an example of how to write your own wrapper types.