Serialize a UniFFI object to JSON from the foreign platform code

[chris13524]

Consumers of my Rust code, in Kotlin and Swift, want to serialize several of our #[uniffi::Record] objects to a JSON string (in order to pass it through yet another layer of FFI). Is this possible currently?

In the docs it looks like UniFFI supports exposing functions from standard Rust crates, however serde::Serialize is not listed here.

I've tried creating a generic helper function to serialize any serializable object. However it looks like #[uniffi::export] doesn't support functions with generic arguments. I could create a separate exported function for each JSON-serializable type, but this would be inconvenient.

For Swift specifically, ideally the generated type implements Encodable.

[mhammond]

As you noted, functions with generic args don't work. While records can't have methods, you could have a namespace function which does the serialize - eg fn serialize_my_record(record: &MyRecord) -> String

Re Encodable, #1905 sketches out a proposal which seems workable, but I don't think anyone has started working on that at this stage.

[chris13524]

you could have a namespace function which does the serialize - eg fn serialize_my_record(record: &MyRecord) -> String

Got it, so I need to make many functions, one for each type they want to serialize.