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Custom encoder/decoders

We can customize how a type is encoded and decoded.

Example​

Suppose we have a FancyRustType and corresponding type FancyDartType (they can be the same name, here we use different names just to make it clearer). If we want to encode it using a String (can use arbitrary complex types as long as flutter_rust_bridge supports), then we can write code like below:

#[frb(rust2dart(dart_type = "FancyDartType", dart_code = "FancyDartType.letsParseIt({})"))]
pub fn encode_fancy_type(raw: FancyRustType) -> String { ... }

#[frb(dart2rust(dart_type = "FancyDartType", dart_code = "{}.letsEncodeIt()"))]
pub fn decode_fancy_type(raw: String) -> FancyRustType { ... }

The function names above are arbitrarily chosen. Then, whenever we are using FancyType, such as:

pub fn f(a: FancyRustType) { ... }

It will be automatically converted to:

void f(FancyDartType a) { ... }

And under the hood, the type will be encoded/decoded via the custom functions.

Remarks​

  • If the Dart types need some imports to work, the dart_preamble config key in flutter_rust_bridge.yaml can be utilized to import things.
  • If the encoding/decoding process returns a Result, currently you can unwrap() it to convert it to a panic.