如何解决如何在 Rust 中使用生命周期参数迭代结构列表？
pub trait TFilterData {
fn get_text(&self) -> &str;
}
pub struct Table<'a> {
pub buf: &'a [u8],pub loc: usize,}
pub struct Data<'a> {
pub _tab: Table<'a>,}
pub struct MatchResult<'a> {
pub _tab: Table<'a>,}
pub struct FiltersByKeyword<'a> {
pub _tab: Table<'a>,}
pub struct KeywordByFilter<'a> {
pub _tab: Table<'a>,}
pub struct BlockingFilter<'a> {
pub _tab: Table<'a>,}
impl TFilterData for BlockingFilter<'_> {
fn get_text(&self) -> &str {
todo!()
}
}
impl<'a> MatchResult<'a> {
pub fn blocking_filters(&self) -> Option<Vec<BlockingFilter<'a>>> {
None
}
}
impl<'a> FiltersByKeyword<'a> {
pub fn filters(&self) -> Option<Vec<MatchResult<'a>>> {
None
}
pub fn keyword(&self) -> String {
"".to_owned()
}
}
impl<'a> Data<'a> {
pub fn keyword_by_filter_list(&self) -> Option<Vec<KeywordByFilter<'a>>> {
None
}
pub fn filters_by_keyword_list(&self) -> Option<Vec<FiltersByKeyword<'a>>> {
None
}
}
我有自己的结构体：
pub type RcedFilterDataVec = Vec<Rc<dyn TFilterData>>;
pub struct FlatBuffersIndex<'a> {
data: Data<'a>,filter_by_keyword: HashMap<String,RcedFilterDataVec>,// keyword -> list of `TFilterData`s
keyword_by_filter: HashMap<String,String>,// Filter -> keyword
}
impl<'a> FlatBuffersIndex<'a> {
pub fn new(buffer: &'a [u8]) -> Self {
let data: Data<'a> = Data {
_tab: Table {
buf: buffer,loc: 0,},};
let mut keyword_by_filter = HashMap::new();
let mut filter_by_keyword = HashMap::new();
if let Some(some_filters_by_keyword_list) = data.filters_by_keyword_list() {
for key_value in some_filters_by_keyword_list {
let mut filters = RcedFilterDataVec::new();
// filters
for each_match_result in key_value.filters().unwrap() {
// Todo: there is no sense in mixing of them as later matcher will have to separate them
// blocking
if let Some(some_blocking_filters) = each_match_result.blocking_filters() {
for each_blocking_filter in some_blocking_filters {
// actually we don't need BlockingFilter part more than RegExpFilter + FilterType
// let filter = each_blocking_filter.regexp_filter().clone();
let rc_filter = Rc::new(each_blocking_filter);
filters.push(rc_filter);
// Todo: add it!!! currently commented due to unclear lifetime issue
}
}
// ...
}
filter_by_keyword.insert(key_value.keyword().to_owned(),filters);
}
}
FlatBuffersIndex {
data,filter_by_keyword,keyword_by_filter,}
}
}
error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
--> src/lib.rs:83:58
|
83 | if let Some(some_filters_by_keyword_list) = data.filters_by_keyword_list() {
| ^^^^^^^^^^^^^^^^^^^^^^^
|
note: first,the lifetime cannot outlive the lifetime `'a` as defined on the impl at 72:6...
--> src/lib.rs:72:6
|
72 | impl<'a> FlatBuffersIndex<'a> {
| ^^
note: ...so that the types are compatible
--> src/lib.rs:83:58
|
83 | if let Some(some_filters_by_keyword_list) = data.filters_by_keyword_list() {
| ^^^^^^^^^^^^^^^^^^^^^^^
= note: expected `&Data<'_>`
found `&Data<'a>`
= note: but,the lifetime must be valid for the static lifetime...
note: ...so that the expression is assignable
--> src/lib.rs:111:13
|
111 | filter_by_keyword,| ^^^^^^^^^^^^^^^^^
= note: expected `HashMap<_,Vec<Rc<(dyn TFilterData + 'static)>>>`
found `HashMap<_,Vec<Rc<dyn TFilterData>>>`
为什么编译器不清楚它会存在于 'a 中，这在这里似乎没问题？我该如何解决？
namespace com.eyeo.adblockplus.fb;
table AbpFilter {
filter_text: string (required); // Strings are UTF-8,[ubyte] might be needed. How will we have `String` without convertions then?
filter_type: ushort;
}
table CommentFilter {
filter: AbpFilter (required);
}
table InvalidFilter {
filter: AbpFilter (required);
reason: string (required);
}
table ActiveFilter {
filter: AbpFilter (required);
sitekeys: [string];
domain_separator: string (required);
domain_source: string;
domain_source_is_lower_case: bool;
}
table RegExpFilter {
active_filter: ActiveFilter (required);
third_party: bool;
content_type: uint;
pattern: string;
rewrite: string;
}
// Probably we don't really need subclasses of RegExpFilter for matching
// as we have RegExpFilter + FilterType to be used by Matcher when matching
table BlockingFilter {
regexp_filter: RegExpFilter (required);
collapse: bool; // probably unneeded
csp: string; // probably unneeded
}
table AllowingFilter {
regexp_filter: RegExpFilter (required);
}
table MatchResult {
blocking_filters: [BlockingFilter];
allowing_filters: [AllowingFilter];
}
// non-abstract filters (leafs)
// vector of union's is not supported unfortunately,// thus we can't declare `filters: [FilterUnion]` in `struct` or `table`. Can we?
// union FilterUnion {
// CommentFilter,// InvalidFilter,// }
table KeywordByFilter {
filter_text: string (required,key);
keyword: string (required);
}
table FiltersByKeyword {
keyword: string (key);
filters: [MatchResult];
}
table Storage {
invalid_filters: [InvalidFilter];
comment_filters: [CommentFilter];
}
table Data {
filters: [MatchResult];
keyword_by_filter_list: [KeywordByFilter];
filters_by_keyword_list: [FiltersByKeyword];
storage: Storage;
}
root_type Data;
PPS。我发现它仅在迭代来自 flatbuffers 集合（each_match_result.blocking_filters() 或 each_match_result.allowing_filters()）的另一个向量并将其添加到放入 filters 的新过滤器向量 filter_by_keyword 中时发生:
if let Some(some_blocking_filters) = each_match_result.blocking_filters() {
for each_blocking_filter in some_blocking_filters {
// actually we don't need BlockingFilter part more than RegExpFilter + FilterType
filters.push(Rc::new(each_blocking_filter.regexp_filter()));
}
}
以下是其他集合的声明方式：
pub fn blocking_filters(&self) -> Option<flatbuffers::Vector<'a,flatbuffers::ForwardsUOffset<BlockingFilter<'a>>>> {
self._tab.get::<flatbuffers::ForwardsUOffset<flatbuffers::Vector<flatbuffers::ForwardsUOffset<BlockingFilter<'a>>>>>(MatchResult::VT_BLOCKING_FILTERS,None)
}
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