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Macro zng_app::event_args

source · 
macro_rules! event_args {
    ($(
        $(#[$outer:meta])*
        $vis:vis struct $Args:ident {
            $($(#[$arg_outer:meta])* $arg_vis:vis $arg:ident : $arg_ty:ty,)*
            ..
            $(#[$delivery_list_outer:meta])*
            fn delivery_list(&$self:ident, $delivery_list_ident:ident: &mut UpdateDeliveryList) { $($delivery_list:tt)* }

            $(
                $(#[$validate_outer:meta])*
                fn validate(&$self_v:ident) -> Result<(), $ValidationError:path> { $($validate:tt)+ }
            )?
        }
    )+) => { ... };
}
Expand description

Declares new EventArgs types.

The macro syntax is similar to struct declaration, but after the args struct members you must add .. and then the fn delivery_list(&self, list: &mut UpdateDeliveryList) {} method that inserts the widget targets.

After the delivery_list method you can also optionally add a fn validate(&self) -> Result<(), Txt> { } method that validates the arguments.

The macro expansion implements the EventArgs and AnyEventArgs traits for the new structs, it generates a public timestamp member and the new associated function that can instantiate args with custom timestamp and propagation handle and the now associated function that provides the timestamp and propagation handle and is the primary way to instantiate args.

§Examples

event_args! {
    /// My event arguments.
    pub struct MyEventArgs {
        /// My argument.
        pub arg: String,
        /// My event target.
        pub target: WidgetPath,

        ..
        
        fn delivery_list(&self, list: &mut UpdateDeliveryList) {
            list.insert_wgt(&self.target);
        }

        /// Optional validation, if defined the generated `new` and `now` functions call it and unwrap the result.
        ///
        /// The error type can be any type that implement `Debug`.
        fn validate(&self) -> Result<(), Txt> {
            if self.arg.contains("error") {
                return Err(formatx!("invalid arg `{}`", self.arg));
            }
            Ok(())
        }
    }

    // multiple structs can be declared in the same call.
    // pub struct MyOtherEventArgs { /**/ }
}