說我有以下內容,如何解決這個與生命週期相關的錯誤?
type EpollEventCallback<'a> = FnMut(c_int) + Send + Sync + 'a;
struct EpollFdEventHandler<'a> {
on_readable: Option<Box<EpollEventCallback<'a>>>,
on_writable: Option<Box<EpollEventCallback<'a>>>,
}
// Map from c_int -> EpollFdEventHandler.
type EpollEventHandlerMap<'a> = collections::HashMap<c_int, EpollFdEventHandler<'a>>;
fn add_fd_handler
<'a, T: Fn(bool, &'a mut EpollFdEventHandler<'a>)>(
map: &'a mut EpollEventHandlerMap<'a>,
fd: c_int,
adder: T)
{
let mut hash_entry: hash_map::Entry<'a, _, _> = map.entry(fd);
match hash_entry {
hash_map::Entry::Occupied(ref mut occ_e) => {
let entry: &mut EpollFdEventHandler<'a> = occ_e.get_mut();
adder(false, entry);
},
hash_map::Entry::Vacant(vac_e) => {
/*
adder(
true,
vac_e.insert(EpollFdEventHandler {
on_readable: None,
on_writable: None,
}),
);
*/
}
};
}
add_fd_handler
被認爲是用於添加「FD處理程序」的輔助功能;在這裏,它將通過關閉(adder
),該關閉會設置on_readable
或on_writable
,具體取決於要添加的處理程序。 add_fd_handler
的工作僅僅是做哈希表查找,並在需要時插入一個空條目。但是:
src/event_loop.rs:85:35: 85:48 error: `(hash_entry:std::collections::hash::map::Occupied).0` does not live long enough
src/event_loop.rs:85 hash_map::Entry::Occupied(ref mut occ_e) => {
^~~~~~~~~~~~~
src/event_loop.rs:82:1: 101:2 note: reference must be valid for the lifetime 'a as defined on the block at 82:0...
src/event_loop.rs:82 {
src/event_loop.rs:83 let mut hash_entry: hash_map::Entry<'a, _, _> = map.entry(fd);
src/event_loop.rs:84 match hash_entry {
src/event_loop.rs:85 hash_map::Entry::Occupied(ref mut occ_e) => {
src/event_loop.rs:86 let entry: &mut EpollFdEventHandler<'a> = occ_e.get_mut();
src/event_loop.rs:87 adder(false, entry);
...
src/event_loop.rs:83:67: 101:2 note: ...but borrowed value is only valid for the block suffix following statement 0 at 83:66
src/event_loop.rs:83 let mut hash_entry: hash_map::Entry<'a, _, _> = map.entry(fd);
src/event_loop.rs:84 match hash_entry {
src/event_loop.rs:85 hash_map::Entry::Occupied(ref mut occ_e) => {
src/event_loop.rs:86 let entry: &mut EpollFdEventHandler<'a> = occ_e.get_mut();
src/event_loop.rs:87 adder(false, entry);
src/event_loop.rs:88 },
約occ_e
該錯誤只顯示了,如果我嘗試使用adder(false, entry)
使用它!鏽索賠occ_e
「活得不夠長」,但它只在match
的分支中使用,那該怎麼做?
我的最好現在猜想是關閉的第二個參數,因爲&'a mut
是什麼問題在這裏;我在occ_e
中的參考不是'a
,它是短一些的(我認爲在hash_entry
上未指定的生命期,但我不知道如何註明)。