问题描述
我正在尝试创建一个结构来管理一个Tokio任务，其中一个if(regularPrice >= discountPrice){
TextSpan(
text: ' $regularPrice',style: TextStyle(
decoration: Textdecoration.lineThrough,decorationThickness: 2.85,fontSize: 15,ontWeight: FontWeight.bold),),TextSpan(
text: ' $discountPrice',style: TextStyle(
fontSize: 15,}else{
TextSpan(
text: ' $regularPrice',}
用来向任务发送输入，一个const categories = [{
"category": "Category 1","desc": "Description 1 of the category 1"
},{
"category": "Category 1","desc": "Description 2 of the category 1"
},{
"category": "Category 2","desc": "Description 1 of the category 2"
},"desc": "Description 2 of the category 2"
},{
"category": "Category 3","desc": "Description 1 of the category 3"
},"desc": "Description 2 of the category 3"
}
];
const newArr = categories.reduce((acc,curr) => {
let target = acc.find(element => element.category === curr.category);
if (target) {
if (!target.descriptionList.includes(curr)) {
delete curr.category;
target.descriptionList.push(curr);
}
} else {
acc.push({
category: curr.category,descriptionList: [{ desc: curr.desc }]
})
}
return acc
},[]);
console.log('newArr: ' + JSON.stringify(newArr));
用来接收来自任务的输出，还有一个我可以处理的句柄最后加入。
newArr: [
{
"category": "Category 1","descriptionList": [
{
"desc": "Description 1 of the category 1"
},{
"desc": "Description 2 of the category 1"
}
]
},"descriptionList": [
{
"desc": "Description 1 of the category 2"
},{
"desc": "Description 2 of the category 2"
}
]
},"descriptionList": [
{
"desc": "Description 1 of the category 3"
},{
"desc": "Description 2 of the category 3"
}
]
}
]
当我尝试对此进行编译时，对于tokio::sync::mpsc::Sender会收到此错误，而对于其他两个类型参数，则会收到类似的错误：
tokio::sync::mpsc::Receiver我很难理解一生的问题所在。以我的理解，生命周期的问题通常来自寿命不长的引用，但是我在移动值，而不是使用引用。我将use tokio::sync::mpsc;
use tokio::task::JoinHandle;
// A type that implements BlockFunctionality consumes instances of T and
// produces either Ok(Some(U)) if an output is ready,Ok(None) if an output
// is not ready,or an Err(_) if the operation fails
pub trait BlockFunctionality<T,U> {
fn apply(&mut self,input:T) -> Result<Option<U>,&'static str>;
}
pub struct Block<T,U> {
pub tx_input: mpsc::Sender<T>,pub rx_output: mpsc::Receiver<U>,pub handle: JoinHandle<Result<(),&'static str>>,}
impl<T: Send,U: Send> Block<T,U> {
pub fn from<B: BlockFunctionality<T,U> + Send>(b:B) -> Self {
let ( tx_input,mut rx_input) = mpsc::channel(10);
let (mut tx_output,rx_output) = mpsc::channel(10);
let handle:JoinHandle<Result<(),&'static str>> = tokio::spawn(async move {
let mut owned_b = b;
while let Some(t) = rx_input.recv().await {
match owned_b.apply(t)? {
Some(u) => tx_output.send(u).await.map_err(|_| "Unable to send output")?,None => (),}
}
Ok(())
});
Block{ tx_input,rx_output,handle }
}
}
，B和 |
22 | pub fn from<B: BlockFunctionality<T,U> + Send>(b:B) -> Self {
| -- help: consider adding an explicit lifetime bound...: `B: 'static +`
...
27 | let handle:JoinHandle<Result<(),&'static str>> = tokio::spawn(async move {
| ^^^^^^^^^^^^ ...so that the type `impl std::future::Future` will meet its required lifetime bounds
移到闭包中，并将b，rx_input和tx_output保留在调用范围内。有谁知道在这种情况下如何满足编译器的要求？
解决方法
这些值可能是引用，也可能包含引用。引用类型是有效类型：B可以是&'a str。或B可以是SomeType<'a>，这是一种带有生命周期参数的类型，它本身包含一个&'a str。
说B: 'static意味着B的所有生存期参数都超过'static（ref）。例如，拥有自己的数据并因此没有生存期参数（例如String）的类型满足此限制。但是&'static str也满足边界。
由于tokio::spawn创建的生命周期不是静态范围的，因此它requires a 'static argument。
因此，要使编译器满意，请添加'static范围：
impl<T: 'static + Send,U: 'static + Send> Block<T,U> {
pub fn from<B: 'static + BlockFunctionality<T,U> + Send>(b:B) -> Self {