英文:
How do you mutate data in Rust Wasm? Getting borrow checker errors
问题
I've translated the provided text for you:
我已经尝试了从 Rc<RefCell> 到 Arc 和 Mutex，async_std 甚至不能编译，尽管它显然包括 wasm 支持。
我已经与这个错误斗争了几天，但我无法理解问题，因为非 wasm 似乎工作正常，而 Promise 没有任何区别。我也尝试了不使用 self，使用没有结构的代码，但问题依然存在。
use std::cell::RefCell;use std::rc::Rc;use wasm_bindgen_futures::spawn_local;use wasm_bindgen::prelude::*;pub struct MyClass {value: u32,}impl MyClass {pub fn new() -> Self {return Self { value: 0 };}pub async fn boot_async(this: Rc<RefCell<&mut Self>>) {this.borrow_mut().value += 1;}pub fn boot(&mut self) {let this = Rc::new(RefCell::new(self));let async_function = MyClass::boot_async(this.clone());spawn_local(async_function);}}#[wasm_bindgen(start)]fn start() {let mut test = MyClass::new();test.boot();}
然后我得到了以下错误：
error[E0521]: borrowed data escapes outside of method--> src/main.rs:29:30|27 | pub fn boot(&mut self) {| ---------| || `self` is a reference that is only valid in the method body| let's call the lifetime of this reference `'1`28 | let this = Rc::new(RefCell::new(self));29 | let async_function = MyClass::boot_async(this.clone());| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^| || `self` escapes the method body here| argument requires that `'1` must outlive `'static`|= note: requirement occurs because of the type `RefCell<&mut MyClass>`, which makes the generic argument `&mut MyClass` invariant= note: the struct `RefCell<T>` is invariant over the parameter `T`= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
英文:
I've tried everything from Rc<RefCell> to Arc and Mutex async_std which wouldn't even compile despite it apparently including wasm support.
I've been fighting with this error for a few days now and I can't fathom the problem when non-wasm seems to work fine and Promise no different. Tried it on not-self as well, using struct-less code, same problem.
use std::cell::RefCell;use std::rc::Rc;use wasm_bindgen_futures::spawn_local;use wasm_bindgen::prelude::*;pub struct MyClass {value: u32,}impl MyClass {pub fn new() -> Self {return Self { value: 0 };}pub async fn boot_async(this: Rc<RefCell<&mut Self>>) {this.borrow_mut().value += 1;}pub fn boot(&mut self) {let this = Rc::new(RefCell::new(self));let async_function = MyClass::boot_async(this.clone());spawn_local(async_function);}}#[wasm_bindgen(start)]fn start() {let mut test = MyClass::new();test.boot();}
And I get:
error[E0521]: borrowed data escapes outside of method--> src/main.rs:29:30|27 | pub fn boot(&mut self) {| ---------| || `self` is a reference that is only valid in the method body| let's call the lifetime of this reference `'1`28 | let this = Rc::new(RefCell::new(self));29 | let async_function = MyClass::boot_async(this.clone());| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^| || `self` escapes the method body here| argument requires that `'1` must outlive `'static`|= note: requirement occurs because of the type `RefCell<&mut MyClass>`, which makes the generic argument `&mut MyClass` invariant= note: the struct `RefCell<T>` is invariant over the parameter `T`= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
答案1
得分: 2
The problem is that Rc doesn't help since you still have a reference. You need to get rid of it:
impl MyClass {pub fn new() -> Self {return Self { value: 0 };}pub async fn boot_async(this: Rc<RefCell<Self>>) {this.borrow_mut().value += 1;}pub fn boot(self) {let this = Rc::new(RefCell::new(self));let async_function = MyClass::boot_async(this.clone());spawn_local(async_function);}}
英文:
Your were close. The problem is that Rc doesn't help since you still have a reference. You need to get rid of it:
impl MyClass {pub fn new() -> Self {return Self { value: 0 };}pub async fn boot_async(this: Rc<RefCell<Self>>) {this.borrow_mut().value += 1;}pub fn boot(self) {let this = Rc::new(RefCell::new(self));let async_function = MyClass::boot_async(this.clone());spawn_local(async_function);}}
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