[Rust][Relm 4]Simple user greet example

README.md

Relm 4 - Greet user example

Rust + GTK4 + Relm

This is a simple example of Relm 4 application where:

• the user can enter its name in a text field
• update the greet message with a button

Cargo.toml

[package]
name = "greet-user"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
gtk = {version = "0.3", package = "gtk4"}
relm4 = "0.2"
relm4-macros = "0.2"
relm4-components = "0.2"

main.rs

use gtk::prelude::{BoxExt, ButtonExt, GtkWindowExt, OrientableExt, EntryExt, EditableExt};
use relm4::{send, AppUpdate, Model, RelmApp, Sender, WidgetPlus, Widgets};

#[derive(Default)]
struct AppModel {
    name: String,
    value: String,
}

enum AppMsg {
    Greet,
    SetName(String),
}

impl Model for AppModel {
    type Msg = AppMsg;
    type Widgets = AppWidgets;
    type Components = ();
}

impl AppUpdate for AppModel {
    fn update(&mut self, msg: AppMsg, _components: &(), _sender: Sender<AppMsg>) -> bool {
        match msg {
            AppMsg::Greet => {
                let substitute = if self.name.len() > 0 {self.name.clone()} else {String::from("")}; 
                self.value = format!("Hello {} !", substitute);
            },
            AppMsg::SetName(new_name) => {
                self.name = new_name;
            }
        }
        true
    }
}

#[relm4_macros::widget]
impl Widgets<AppModel, ()> for AppWidgets {
    view! {
        gtk::ApplicationWindow {
            set_title: Some("Greet user"),
            set_default_width: 300,
            set_default_height: 200,
            set_child = Some(&gtk::Box) {
                set_orientation: gtk::Orientation::Vertical,
                set_margin_all: 5,
                set_spacing: 5,

                append = &gtk::Box {
                    set_spacing: 10,
                    set_orientation: gtk::Orientation::Horizontal,
                    append: name_entry = &gtk::Entry {
                        set_placeholder_text: Some("Your name"),
                        connect_changed(sender) => move |name_entry| {
                            send!(sender, AppMsg::SetName(format!("{}", name_entry.text())));
                        }
                    },
                    append = &gtk::Button {
                        set_label: "Let CPU greet",
                        connect_clicked(sender) => move |_| {
                            send!(sender, AppMsg::Greet);
                        }
                    }
                },
                append = &gtk::Label {
                    set_margin_all: 5,
                    set_label: watch! { model.value.as_str() },
                }
            },
        }
    }
}

fn main() {
    let model = AppModel::default();
    let app = RelmApp::new(model);
    app.run();
}

Preview.png