producing_messages_by_timers.md

Producing Messages By Timers

To use build-in timers, we need to enable one of the following features: tokio, async-std, or smol. In this tutorial, we use tokio feature. The dependencies of Cargo.toml should look like this:

[dependencies]
iced = { version = "0.12.1", features = ["tokio"] }

We use time::every function to obtain Subscription<Instant> struct. Then we map the struct to Subscription<MyAppMessage> by Subscription::map method. The result will be returned in the subscription method of Application. The corresponding MyAppMessage will be received in the update method.

use iced::{
    executor,
    time::{self, Duration},
    widget::text,
    Application, Command, Settings,
};

fn main() -> iced::Result {
    MyApp::run(Settings::default())
}

#[derive(Debug, Clone)]
enum MyAppMessage {
    Update,
}

struct MyApp {
    seconds: u32,
}

impl Application for MyApp {
    type Executor = executor::Default;
    type Message = MyAppMessage;
    type Theme = iced::Theme;
    type Flags = ();

    fn new(_flags: Self::Flags) -> (Self, iced::Command<Self::Message>) {
        (Self { seconds: 0 }, Command::none())
    }

    fn title(&self) -> String {
        String::from("My App")
    }

    fn update(&mut self, message: Self::Message) -> iced::Command<Self::Message> {
        match message {
            MyAppMessage::Update => self.seconds += 1,
        }
        Command::none()
    }

    fn view(&self) -> iced::Element<Self::Message> {
        text(self.seconds).into()
    }

    fn subscription(&self) -> iced::Subscription<Self::Message> {
        time::every(Duration::from_secs(1)).map(|_| MyAppMessage::Update)
    }
}

➡️ Next: Batch Subscriptions

📘 Back: Table of contents