[英]Fighting with the Rust borrow checker
This code looks like it would work fine to me, but the rust borrow checker doesn't like it: 这段代码对我来说似乎可以正常工作,但是rust借用检查器不喜欢它:
extern crate rustbox;
use std::error::Error;
use std::default::Default;
use rustbox::{Color, RustBox};
use rustbox::Key;
use std::fs::File;
use std::env;
use std::io::BufReader;
use std::io::BufRead;
fn display_screenful(rb: &RustBox, fr: BufReader<&'static File>, offset: usize) {
for (rline, idx) in fr.lines().zip(0..).skip(offset).take(rb.height()) {
match rline {
Ok(line) => (*rb).print(0, idx, rustbox::RB_NORMAL, Color::White, Color::Black, &line),
Err(_) => (*rb).print(0, idx, rustbox::RB_NORMAL, Color::White, Color::Black, "")
}
}
}
fn main() {
let rustbox = match RustBox::init(Default::default()) {
Ok(v) => v,
Err(e) => panic!(e),
};
let path = env::args().nth(1).unwrap();
let file = match File::open(&path) {
Ok(file) => file,
Err(e) => panic!(e)
};
let file_reader = BufReader::new(&file);
display_screenful(&rustbox, file_reader, 0);
rustbox.present();
loop {
match rustbox.poll_event(false) {
Ok(rustbox::Event::KeyEvent(key)) => {
match key {
Some(Key::Char('q')) => { break; }
Some(Key::Char(' ')) => {
display_screenful(&rustbox, file_reader, rustbox.height());
rustbox.present();
}
_ => { }
}
},
Err(e) => panic!("{}", e.description()),
_ => { }
}
}
}
I guess I could not use a separate function, and use two for loop parts, instead, but that isn't idiomatic Rust, nor is it good coding practice. 我想我不能使用一个单独的函数,而是使用两个for循环部分,但这不是惯用的Rust,也不是很好的编码习惯。 In fact, I've tried that, but it just tells me that I'm using a moved value.
实际上,我已经尝试过了,但这只是告诉我我正在使用移动值。 Here are some errors that I'm getting:
这是我遇到的一些错误:
Compiling rusted v0.1.0 (file:///Users/christopherdumas/rusted)
src/main.rs:34:39: 34:43 error: `file` does not live long enough
src/main.rs:34 let file_reader = BufReader::new(&file);
^~~~
note: reference must be valid for the static lifetime...
src/main.rs:33:7: 55:2 note: ...but borrowed value is only valid for the block suffix following statement 2 at 33:6
src/main.rs:33 };
src/main.rs:34 let file_reader = BufReader::new(&file);
src/main.rs:35
src/main.rs:36 display_screenful(&rustbox, file_reader, 0);
src/main.rs:37 rustbox.present();
src/main.rs:38
...
src/main.rs:45:53: 45:64 error: use of moved value: `file_reader` [E0382]
src/main.rs:45 display_screenful(&rustbox, file_reader, rustbox.height());
^~~~~~~~~~~
src/main.rs:45:53: 45:64 help: run `rustc --explain E0382` to see a detailed explanation
src/main.rs:36:33: 36:44 note: `file_reader` moved here because it has type `std::io::buffered::BufReader<&'static std::fs::File>`, which is non-copyable
src/main.rs:36 display_screenful(&rustbox, file_reader, 0);
^~~~~~~~~~~
error: aborting due to 2 previous errors
Could not compile `rusted`.
To learn more, run the command again with --verbose.
Firstly, you shouldn't ask for a BufReader<&'static File>
. 首先,您不应该要求提供
BufReader<&'static File>
。 You can't provide one. 您无法提供。 Ask instead for a
BufReader<&'a File>
for some lifetime 'a
. 而是要求一个
BufReader<&'a File>
一生中的时间'a
。
fn display_screenful<'a>(rb: &RustBox, fr: BufReader<&'a File>, offset: usize)
or, for short, 或者,简而言之,
fn display_screenful(rb: &RustBox, fr: BufReader<&File>, offset: usize)
That's not enough either - you then end up moving file_reader
into the function. 这也不足够-然后您最终将
file_reader
移入函数中。 You should borrow instead: 您应该改为借用:
fn display_screenful(rb: &RustBox, fr: &mut BufReader<&File>, offset: usize)
and then it compiles. 然后编译。
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