我可能遗漏了一些非常基本的东西——我是 Rust 的新手。我正在尝试将petgraph::dot::Dot
表示写入文件。
以下小代码示例无法编译:
use petgraph::Graph;
use petgraph::dot::{Dot, Config};
use std::fs::File;
use std::io::Write;
fn main() {
println!("hello graph!");
let mut graph = Graph::<_, ()>::new();
graph.add_node("A");
graph.add_node("B");
graph.add_node("C");
graph.add_node("D");
graph.extend_with_edges(&[
(0, 1), (0, 2), (0, 3),
(1, 2), (1, 3),
(2, 3),
]);
println!("{:?}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
let mut f = File::create("example1.dot").unwrap();
let output = format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
f.write_all(&output.as_bytes());
}
这是编译器错误输出:
error[E0277]: `()` doesn't implement `std::fmt::Display`
--> examples/graphviz.rs:21:32
|
21 | let output = format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` cannot be formatted with the default formatter
|
= help: the trait `std::fmt::Display` is not implemented for `()`
= note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
= note: required because of the requirements on the impl of `std::fmt::Display` for `petgraph::dot::Dot<'_, &petgraph::graph_impl::Graph<&str, ()>>`
= note: required by `std::fmt::Display::fmt`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0277`.
petgraph 文档指出Dot 实现了 Display 特征,我的代码基于trait.Display 文档中的示例代码
我可以通过将格式字符串更改为来使代码工作,{:?}
但我认为这只是为了调试。有没有更好的方法来编写代码来完成同样的事情?