How to send events between flutter and rust

[TibiToz]

Hey !

What would be the simplest way of passing events between Rust and Flutter.

Rust is scanning for iot devices on my network and I would like to send async events with some data when a new device is discovered or when a device is disconnected to update accordingly my UI in flutter.

Is it possible to directly use an mpsc channel or an async::mpscchannel from tokio ?

I'm not sure how about to proceed with this.

Any ideas to get me started is very welcome :)

T.

[fzyzcjy]

Hi, what about a Stream https://cjycode.com/flutter_rust_bridge/guides/types/translatable/stream ?

[TibiToz]

I managed to send some events with stream, thank you.

But it seems that i struggle to retrieve the data in Flutter, maybe you can help me better understand the problem:

I have something like this :

pub struct Device {
    hostname: String,
    ip: HashSet<IpAddr>,
}


pub enum DeviceEvent {
    New(Device),
    Removed(Device),
    Connected(Device),
    Disconnected(Device),
    Error(String),
}

fn send_event ( e:  DeviceEvent<Device>) {
   stream.add(e)
}

On the flutter side I want to be able to match and retrieve data of specific event. But I don't understand how, even after reading the documentation.

[TibiToz]

I understood my mistake, I treated enum like structs.

I had to add #[frb(non_opaque)] on my enum and install freezed.

But it seems that freezed is getting a parsing error. Any ideas how to solve this issue ?

An error FormatterException occurred while formatting the generated source for
package:app/src/rust/api/discovery.dart
which was output to
lib/src/rust/api/discovery.freezed.dart.
This may indicate an issue in the generator, the input source code, or in the
source formatter.
Could not format because the source could not be parsed:

line 21, column 91 of .: Expected to find ')'.
╷
21 │ @optionalTypeArgs TResult when<TResult extends Object?>(TResult Function( Device field0) new,{required TResult Function( Device field0) removed,required TResult Function( Device field0) connected,required TResult Function( Device field0) disconnected,required TResult Function( String field0) error,}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 22, column 100 of .: Expected to find ')'.
╷
22 │ @optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? Function( Device field0)? new,{TResult? Function( Device field0)? removed,TResult? Function( Device field0)? connected,TResult? Function( Device field0)? disconnected,TResult? Function( String field0)? error,}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 23, column 97 of .: Expected to find ')'.
╷
23 │ @optionalTypeArgs TResult maybeWhen<TResult extends Object?>(TResult Function( Device field0)? new,{TResult Function( Device field0)? removed,TResult Function( Device field0)? connected,TResult Function( Device field0)? disconnected,TResult Function( String field0)? error,required TResult orElse(),}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 24, column 98 of .: Expected to find ')'.
╷
24 │ @optionalTypeArgs TResult map<TResult extends Object?>(TResult Function( DeviceEvent_New value) new,{required TResult Function( DeviceEvent_Removed value) removed,required TResult Function( DeviceEvent_Connected value) connected,required TResult Function( DeviceEvent_Disconnected value) disconnected,required TResult Function( DeviceEvent_Error value) error,}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 25, column 107 of .: Expected to find ')'.
╷
25 │ @optionalTypeArgs TResult? mapOrNull<TResult extends Object?>(TResult? Function( DeviceEvent_New value)? new,{TResult? Function( DeviceEvent_Removed value)? removed,TResult? Function( DeviceEvent_Connected value)? connected,TResult? Function( DeviceEvent_Disconnected value)? disconnected,TResult? Function( DeviceEvent_Error value)? error,}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 26, column 104 of .: Expected to find ')'.
╷
26 │ @optionalTypeArgs TResult maybeMap<TResult extends Object?>(TResult Function( DeviceEvent_New value)? new,{TResult Function( DeviceEvent_Removed value)? removed,TResult Function( DeviceEvent_Connected value)? connected,TResult Function( DeviceEvent_Disconnected value)? disconnected,TResult Function( DeviceEvent_Error value)? error,required TResult orElse(),}) => throw _privateConstructorUsedError;
│ ^^^
╵
line 112, column 91 of .: Expected to find ')'.
╷
112 │ @optionalTypeArgs TResult when<TResult extends Object?>(TResult Function( Device field0) new,{required TResult Function( Device field0) removed,required TResult Function( Device field0) connected,required TResult Function( Device field0) disconnected,required TResult Function( String field0) error,}) {
│ ^^^
╵
line 113, column 13 of .: Expected an identifier.
╷
113 │ return new(field0);
│ ^
╵
line 116, column 100 of .: Expected to find ')'.
╷
116 │ @optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? Function( Device field0)? new,{TResult? Function( Device field0)? removed,TResult? Function( Device field0)? connected,TResult? Function( Device field0)? disconnected,TResult? Function( String field0)? error,}) {
│ ^^^
╵
line 117, column 13 of .: Expected an identifier.
╷
117 │ return new?.call(field0);
│ ^^
╵
(38 more errors...)

[fzyzcjy]

Hi, could you please provide a minimal reproducible sample? Then maybe this can be debugged.

[TibiToz]

Hi, I found the problem.

New must be a reserved keyword, I change my rust enum DeviceEvent::New to something else and it worked