为实现的函数Rust内部的自结构赋值

Question

我最近为一个项目切换到rust，我很难处理可变和不可变的对象。

我遇到了一个问题，我需要将一个可变对象传递给我的一个特性的实现函数中的一个函数。我得到的错误如下：

error[E0596]: cannot borrow `self.volume_name` as mutable, as it is behind a `&` reference
--> src/main.rs:107:40
|
94  |     fn load_info(&self, name: &str) {
|                  ----- help: consider changing this to be a mutable reference: `&mut self`
...
107 |         seek_read(&mut opened_file, 3, &mut self.volume_name).unwrap();
|                                        ^^^^^^^^^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable

我不知道如何修复这个错误，因为我尝试的每一个修复都会弹出另一个错误。我试着创建一个新对象，并将新对象设置为self，但这也不起作用，因为这个函数中的self是一个引用，如果我在离开上下文后将地址设置为相同，它就会消失，所以我又犯了一个错误！记住，我来自C.

基本代码：

pub trait Filesystem {
fn load_info(&self, name: &str);
}
pub struct Fat16 {
pub volume_name: [u8; 8],
}
impl Default for Fat16 {
fn default() -> Fat16 {
Fat16 {
volume_name: [0; 8],
}
}
}
impl Filesystem for Fat16 {
fn load_info(&self, name: &str) {
//I assume the file is a Fat16 volume, the checks are done before
let mut opened_file = match File::open(&name) {
Err(why) => panic!("couldn't open {}: {}", name, why),
Ok(opened_file) => opened_file,
};
// ------------------------ VOLUME NAME ------------------------
// Volume name starts at 3
seek_read(&mut opened_file, 3, &self.volume_name).unwrap();
match str::from_utf8(&self.volume_name) {
Ok(v) => println!("Volume Name: {}", v),
Err(e) => panic!("Invalid UTF-8 sequence: {}", e),
};

/*more code*/

寻道读取功能：

pub fn seek_read(mut reader: impl Read + Seek, offset: u64, buf: &mut [u8]) -> io::Result<()> {
reader.seek(SeekFrom::Start(offset))?;
reader.read_exact(buf)?;
Ok(())
}

Answer 1

self是&引用，因此它引用的数据不能作为可变借用

推测load_info将把信息加载到Filesystem对象中。如果你想改变self的属性，它必须是可变的。

pub trait Filesystem {
fn load_info(&mut self, name: &str);
^^^^
}
impl Filesystem for Fat16 {
fn load_info(&mut self, name: &str) {
^^^^
let mut opened_file = match File::open(&name) {
Err(why) => panic!("couldn't open {}: {}", name, why),
Ok(opened_file) => opened_file,
};
seek_read(&mut opened_file, 3, &mut self.volume_name).unwrap();
^^^^
match std::str::from_utf8(&self.volume_name) {
Ok(v) => println!("Volume Name: {}", v),
Err(e) => panic!("Invalid UTF-8 sequence: {}", e),
};
}
}