我应该如何减少 Rust 类型签名的重复? [英] How should I reduce repetition in rust type signatures?
问题描述
我有以下不是很干的工作代码:
I have the following working code that isn't very DRY:
impl<'a, G, E, N, EW, NW, ER, NOW, EOW> Overlay<'a, G, E, N, EW, NW, ER, NOW, EOW>
where
&'a G: GraphBase<EdgeId = E, NodeId = N> +
Data<EdgeWeight = EW, NodeWeight = NW> +
DataMap,
ER: EdgeRef<Weight = EW, EdgeId = E, NodeId = N>,
E: Copy + Eq + Hash,
N: Copy + Eq + Hash,
{
fn overlayed_elements(&'a self) -> OverlayedItems<'a, G, E, N, EW, NW, ER, NOW, EOW>{
OverlayedItems{
overlay: self,
phase: Phase::Nodes(self.nodes.iter()),
node_indexes: HashMap::new(),
}
}
pub fn overlay_edge<'b>(&'b mut self, edge: ER, eow: EOW) {
self.edges.insert(edge.id(), eow);
self.edge_refs.insert(edge.id(), edge);
}
pub fn overlay_node<'b>(&'b mut self, node: N, now: NOW) {
self.nodes.insert(node, now);
}
fn remove_edge<'b>(&'b mut self, edge: E) {
self.edges.remove(&edge);
self.edge_refs.remove(&edge);
}
fn remove_node<'b>(&'b mut self, node: N) {
self.nodes.remove(&node);
}
}
我有很多重复的<'a, G, E, N, EW, NW, ER, NOW, EOW>
并且通常似乎所有这些特质thingamamagigs都在使用很多空间.这只是糟糕的代码,还是我做错了什么?
I have a lot of repetition of <'a, G, E, N, EW, NW, ER, NOW, EOW>
and it generally seems that all these trait thingamagigs are taking up a lot of space. Is this just bad code, or am I doing something wrong?
推荐答案
关联类型并不总是需要有自己的类型参数.例如,您可以在绑定中编写 G::EdgeId
而不是具有单独的参数 E
.
Associated types do not always need to have their own type parameters. For example, you can write G::EdgeId
in a bound instead of having a separate parameter E
.
我调整了操场链接中的代码以减少类型参数的数量.这是更新链接例如,Overlay
现在有 4 个而不是 8 个类型参数:
I adjusted the code in the playground link to reduce the number of type arguments. Here's the updated link. For example, Overlay
now has 4 instead of 8 type arguments:
pub struct Overlay<G, ER, NOW, EOW>
where
G: GraphBase + Data,
ER: EdgeRef<Weight = G::EdgeWeight, EdgeId = G::EdgeId, NodeId = G::NodeId>,
{
nodes: HashMap<G::NodeId, NOW>,
edges: HashMap<G::EdgeId, EOW>,
edge_refs: HashMap<G::EdgeId, ER>,
graph: G,
}
请注意,我删除了 G::NodeId
和 G::EdgeId
的(不必要的)Copy + Eq + Hash
特征边界.此外,G
不再落后于特征边界中的引用,这可能会导致生命周期问题,但如果需要,可以修复这些问题.
Note that I removed the (unnecessary) Copy + Eq + Hash
trait bounds for G::NodeId
and G::EdgeId
. Also, G
is no longer behind a reference in the trait bounds, which might cause lifetime issues, but these can be fixed if necessary.
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