Module zng::handler

source ·
Expand description

Event handler API.

A handler is a closure that takes a context and arguments, the context can be WIDGET or the app, handler types implement WidgetHandler or AppHandler respectively. These traits allow a single caller to support multiple different flavors of handlers, both synchronous and asynchronous, and both FnMut and FnOnce all by implementing a single entry point.

Macros are provided for declaring the various flavors of handlers, hn!, hn_once!, async_hn!, async_hn_once! for widget contexts and app_hn!, app_hn_once!, async_app_hn!, async_app_hn_once! for the app context. These macros also build on top of the primitive macros clmv!, async_clmv_fn! and async_clmv_fn_once! to provide a very easy way to clone-move captured variables into the handler.

use zng::prelude::*;

let last_clicked = var(Txt::from(""));
Stack!(top_to_bottom, 5, ui_vec![
    Button! {
        child = Text!("hn!");
        on_click = hn!(last_clicked, |_| {
            last_clicked.set("hn!");
        });
    },
    Button! {
        child = Text!("hn_once!");
        on_click = hn_once!(last_clicked, |_| {
            last_clicked.set("hn_once!");
        });
    },
    {
        let enabled = var(true);
        Button! {
            child = Text!("async_hn!");
            on_click = async_hn!(last_clicked, enabled, |_| {
                last_clicked.set("async_hn!");
                enabled.set(false);
                task::deadline(1.secs()).await;
                enabled.set(true);
            });
            widget::enabled;
        }
    },
    Text!(last_clicked),
])

§Full API

See zng_app::handler for the full handler API.

Macros§

  • app_hn
    Declare a mutable clone-move app event handler.
  • app_hn_once
    Declare a clone-move app event handler that is only called once.
  • async_app_hn
    Declare an async clone-move app event handler.
  • async_app_hn_once
    Declare an async clone-move app event handler that is only called once.
  • async_hn
    Declare an async clone-move event handler.
  • async_hn_once
    Declare an async clone-move event handler that is only called once.
  • hn
    Declare a mutable clone-move event handler.
  • hn_once
    Declare a clone-move event handler that is only called once.

Structs§

Traits§