我有一个受RwLock
保护的全局WORLD
,并且我想编写一个函数,该函数读取该锁并返回一个迭代器(类型为Neighbors
),该迭代器在{ {1}}存储在全局内部。我正在使用petgraph::stable_graph::StableGraph
来处理函数退出后保持读锁保护保持活动的状态,这在过去仅直接返回OwningRef
字段时对我有用。我已经提供了一个可编译的示例,并且出现了下面的错误-似乎存在某种类型问题,但我无法弄清楚。我认为这可能与World
想要处理一个引用而不是一个包含引用(OwningRef
的对象)有关,但是我不确定如何解决。
Cargo.toml:
Neighbors
main.rs:
[package]
name = "problem_demo"
version = "0.1.0"
authors = ["Joseph Garvin <joseph.h.garvin@gmail.com>"]
edition = "2018"
[dependencies]
owning_ref="0.4.1"
once_cell="1.4.0"
petgraph={version="0.5.1", features=["serde-1"]}
错误:
use std::{sync::RwLock};
use once_cell::sync::OnceCell;
use owning_ref::RwLockReadGuardRef;
use petgraph::stable_graph::{StableGraph, Neighbors};
struct Bar {
data: i32
}
struct World {
graph: StableGraph<(), Bar, petgraph::Directed, u32>
}
pub static WORLD: OnceCell<RwLock<World>> = OnceCell::new();
fn neighbors(id: u32) -> Result<RwLockReadGuardRef<'static, World, Neighbors<'static, Bar, u32>>, Box<dyn std::error::Error>> {
RwLockReadGuardRef::new(WORLD.get().unwrap().read().unwrap())
.try_map(
|world: &World| -> std::result::Result<Neighbors<'static, Bar, u32>, Box<dyn std::error::Error>>
{
let neighbors = world.graph.neighbors_directed(
petgraph::graph::NodeIndex::new(id as usize),
petgraph::Direction::Outgoing
);
Ok(neighbors)
}
)
}