Trait dptree::HandlerDescription

source · [−]

pub trait HandlerDescription: Sized + Send + Sync + 'static {
Show 13 methods
    fn entry() -> Self;
    fn user_defined() -> Self;
    fn merge_chain(&self, other: &Self) -> Self;
    fn merge_branch(&self, other: &Self) -> Self;

    fn map() -> Self { ... }
    fn map_async() -> Self { ... }
    fn filter() -> Self { ... }
    fn filter_async() -> Self { ... }
    fn filter_map() -> Self { ... }
    fn filter_map_async() -> Self { ... }
    fn inspect() -> Self { ... }
    fn inspect_async() -> Self { ... }
    fn endpoint() -> Self { ... }
}

Expand description

Handler description.

This trait allows information to flow “back up” the tree, allowing to check its structure.

Examples

Count how many branches are in the tree:

use dptree::{prelude::DependencyMap, Handler, HandlerDescription};

struct CountBranches(u32);

impl HandlerDescription for CountBranches {
    fn entry() -> Self {
        Self(0)
    }

    fn user_defined() -> Self {
        Self(0)
    }

    fn merge_chain(&self, other: &Self) -> Self {
        Self(self.0 + other.0)
    }

    fn merge_branch(&self, other: &Self) -> Self {
        Self(self.0 + other.0 + 1)
    }
}

#[track_caller]
fn assert_count(count: u32, handler: Handler<DependencyMap, (), CountBranches>) {
    assert_eq!(handler.description().0, count);
}

assert_count(0, dptree::entry());
assert_count(1, dptree::entry().branch(dptree::entry()));
assert_count(
    5,
    dptree::entry()
        .branch(
            dptree::entry()
                .branch(dptree::entry().branch(dptree::filter(|| true)))
                .branch(dptree::entry().chain(dptree::filter(|| false))),
        )
        .branch(dptree::entry()),
);