Struct containing reference to a file in Rust fails to borrow - rust

Question

Not sure what I am missing here, the lifetime is declared, therefore the struct should use the path to create the file and return a Struct with the mutable File reference for me to be able to call "write" wrapper later...
use std::path::Path;
use std::fs::File;
// use std::io::Write;
#[derive(Debug)]
pub struct Foo<'a> {
file: &'a mut File,
}
impl<'a> Foo<'a> {
pub fn new(path: &'a Path) -> Result<Self, std::io::Error> {
let mut f: &'a File = &File::create(path)?;
Ok(Self { file: &mut f })
}
//pub fn write(&self, b: [u8]) {
// self.file.write(b);
//}
}
Error:
| impl<'a> Foo<'a> {
| -- lifetime `'a` defined here
11 | pub fn new(path: &'a Path) -> Result<Self, std::io::Error> {
12 | let mut f: &'a File = &File::create(path)?;
| -------- ^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'a`
...
15 | }
| - temporary value is freed at the end of this statement

Answer 1

As #E_net4 mentioned, I don't want a mutable reference, yet I want to own the value. Rather than trying to play with lifetimes, I can basically just own the file and handle the whole struct as mutable when trying to write to the file!
use std::path::{ PathBuf };
use std::fs::File;
use std::io::Write;
use std::env;
#[derive(Debug)]
pub struct Foo {
file: File,
}
impl Foo {
pub fn new(path: PathBuf) -> Self {
Self {
file: File::create(path).unwrap(),
}
}
pub fn write(&mut self, b: &[u8]) -> Result<usize, std::io::Error> {
self.file.write(b)
}
}
fn main() {
let mut tmp_dir = env::temp_dir();
tmp_dir.push("foo23");
let mut f = Foo::new(tmp_dir);
f.write(b"test2").unwrap();
}