如何在Yew Hook中返回状态的字符串值？解决use_effect_with_deps报错

原问题代码 #

use std::ops::Deref;
use yew::prelude::*;

#[hook]
pub fn use_hook_test() -> String
{
    let first_load = use_state(|| true);

    let hash_state = use_state(|| "".to_owned());

 
    let hash_state_clone = hash_state.clone();
    use_effect_with_deps(move |_| {
        if *first_load {
            wasm_bindgen_futures::spawn_local(async move {

                    hash_state_clone.set(format!("{:?}", "Hello"));
                
            });

            first_load.set(false);
        }
        || {};
    }, ());

    hash_state_clone.deref().clone()
}

编译报错信息 #

let hash_state_clone = hash_state.clone();
   |         ---------------- move occurs because `hash_state_clone` has type `yew::UseStateHandle<std::string::String>`, which does not implement the `Copy` trait
14 |     use_effect_with_deps(move |_| {
   |                          -------- value moved into closure here
...
18 |                     hash_state_clone.set(format!("{:?}", "Hello"));
   |                     ---------------- variable moved due to use in closure
...
27 |     hash_state_clone.deref().clone()
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ value borrowed here after move

解决方案及修正代码 #

问题核心是hash_state_clone被移动进use_effect_with_deps的闭包后，所有权已转移，无法在闭包外继续使用。我们需要为闭包单独克隆状态句柄，避免所有权冲突：

use std::ops::Deref;
use yew::prelude::*;

#[hook]
pub fn use_hook_test() -> String
{
    let first_load = use_state(|| true);
    let hash_state = use_state(|| "".to_owned());

    // 为effect闭包单独克隆状态句柄，让闭包拥有独立所有权
    let hash_state_effect = hash_state.clone();
    let first_load_effect = first_load.clone();
    use_effect_with_deps(move |_| {
        if *first_load_effect {
            wasm_bindgen_futures::spawn_local(async move {
                hash_state_effect.set(format!("{:?}", "Hello"));
            });

            first_load_effect.set(false);
        }
        || {}
    }, ());

    // 直接基于原状态句柄返回字符串克隆，无所有权问题
    hash_state.deref().clone()
}

关键说明 #

• UseStateHandle是基于Arc实现的轻量句柄，克隆操作几乎无性能开销，无需担心重复克隆的问题。
• 为闭包单独克隆first_load_effect是因为原first_load属于当前渲染周期的变量，闭包需要拥有自己的句柄才能在异步操作中安全访问。
• 返回部分也可以简化为(**hash_state).clone()或hash_state.to_string()，效果完全一致。

内容的提问来源于stack exchange，提问作者Amiya Behera