rust - 我如何访问 Rust 目录中的文件？

Question

我已经根据 Rust docs 编写了一个非常简单的脚本:

use std::fs::{self, DirEntry};
use std::path::Path;

fn main() {
    let path = Path::new(".");
    for entry in fs::read_dir(path)? {
        let entry = entry?;
        let path = entry.path();
        if path.is_dir() {
            println!("directory found!");
        }
    }

}

但是我得到以下关于 ? 的编译错误:

error[E0277]: the trait bound `(): std::ops::Carrier` is not satisfied
 --> test.rs:6:18
  |
6 |     for entry in fs::read_dir(path)? {
  |                  -------------------
  |                  |
  |                  the trait `std::ops::Carrier` is not implemented for `()`
  |                  in this macro invocation
  |
  = note: required by `std::ops::Carrier::from_error`

error[E0277]: the trait bound `(): std::ops::Carrier` is not satisfied
 --> test.rs:7:21
  |
7 |         let entry = entry?;
  |                     ------
  |                     |
  |                     the trait `std::ops::Carrier` is not implemented for `()`
  |                     in this macro invocation
  |
  = note: required by `std::ops::Carrier::from_error`

我只部分理解 ? 但我知道要点是它允许您仅在 Ok 时对 Result 采取行动。这里的错误是它被用在 () 而不是 Result 上，这很奇怪。我尝试在没有 ? 的情况下实现循环:

use std::fs::{self, DirEntry};
use std::path::Path;

fn main() {
    let path = Path::new(".");
    for entry in fs::read_dir(path) {
        println!("{}", entry.path());
    }

}

但是我得到了错误:

error: no method named `path` found for type `std::fs::ReadDir` in the current scope
 --> test.rs:7:30
  |
7 |         println!("{}", entry.path());
  |                              ^^^^

这意味着 fs::read_dir 返回的 ReadDir 是 DirEntry 项的迭代器，fs::read_dir 正在返回 ()，它在某种程度上是 ReadDir 项的迭代器？

我很困惑。

可能值得一提的是我正在运行:rustc 1.16.0 (30cf806ef 2017-03-10)

Answer 1

第一个错误是because you cannot use try! or ? in a function returning () .

第二个错误是因为read_dir返回了一个Result:

pub fn read_dir<P: AsRef<Path>>(path: P) -> Result<ReadDir>

Result implements IntoIterator ，所以 path 实际上是您认为您拥有的迭代器。

Handling the errors并调用 Path::display 得到你想要的:

use std::fs;
use std::path::Path;

fn main() {
    let path = Path::new(".");
    for entry in fs::read_dir(path).expect("Unable to list") {
        let entry = entry.expect("unable to get entry");
        println!("{}", entry.path().display());
    }
}