Struct zng_app::widget::builder::PropertyInputTypes

pub struct PropertyInputTypes<Tuple>(/* private fields */);

Represents the strong types of each input of a property.

Examples

The example uses property_input_types! to collect the types and compares it to a manually generated types. Note that the type is a tuple even if there is only one input.

#[property(CONTEXT)]
pub fn foo(child: impl UiNode, bar: impl IntoVar<bool>) -> impl UiNode {
}

assert_eq!(
    property_input_types!(foo).type_id(),
    PropertyInputTypes::<(BoxedVar<bool>,)>::unit().type_id(),
);

You can use the collected types in advanced code generation, such as attribute proc-macros targeting property assigns in widgets. The next example demonstrates a trait that uses auto-deref to convert a trait bound to a bool:

#[property(CONTEXT)]
pub fn foo(child: impl UiNode, bar: impl IntoVar<bool>) -> impl UiNode {
}

trait SingleBoolVar {
    fn is_single_bool_var(self) -> bool;
}

// match
impl<'a, V: Var<bool>> SingleBoolVar for &'a PropertyInputTypes<(V,)> {
    fn is_single_bool_var(self) -> bool {
        true
    }
}

// fallback impl
impl<T: Send + 'static> SingleBoolVar for PropertyInputTypes<T> {
    fn is_single_bool_var(self) -> bool {
        false
    }
}

assert!((&property_input_types!(foo)).is_single_bool_var());

Learn more about how this trick works and limitations here.

Implementations

impl<Tuple> PropertyInputTypes<Tuple>

pub const fn unit() -> Self

Unit value.

Trait Implementations

impl<Tuple> Clone for PropertyInputTypes<Tuple>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Tuple> Copy for PropertyInputTypes<Tuple>

impl<Tuple> Send for PropertyInputTypes<Tuple>

impl<Tuple> Sync for PropertyInputTypes<Tuple>