Module value_bag::fill

Deferred value initialization.

The Fill trait is a way to bridge APIs that may not be directly compatible with other constructor methods.

The Fill trait is automatically implemented for closures, so can usually be used in libraries that can’t implement the trait themselves.

use value_bag::{ValueBag, fill::Slot};

let value = ValueBag::from_fill(&|slot: &mut Slot| {
    #[derive(Debug)]
    struct MyShortLivedValue;

    slot.fill_debug(&MyShortLivedValue)
});

assert_eq!("MyShortLivedValue", format!("{:?}", value));

The trait can also be implemented manually:

use value_bag::{ValueBag, Error, fill::{Slot, Fill}};

struct FillDebug;

impl Fill for FillDebug {
    fn fill(&self, slot: &mut Slot) -> Result<(), Error> {
        slot.fill_debug(&42i64 as &dyn Debug)
    }
}

let value = ValueBag::from_fill(&FillDebug);

assert_eq!(None, value.to_i64());

Structs

Slot	A value slot to fill using the Fill trait.

Traits

Fill	A type that requires extra work to convert into a ValueBag.