Questions tagged [lifetime-scoping]
97 questions
4
votes
1 answer
"does not live long enough" error when calling `roots` from rust-xcb
I'm trying to use a Cairo surface in xcb-created window. I have a C example as well as Rust XCB and Cairo bindings. I'm almost finished, but this error remains a mystery to me.
My code:
fn find_visual<'a>(conn: &'a xcb::Connection, visual:…
dimcha
- 193
- 14
3
votes
1 answer
Cast requires that variable is borrowed for 'static
pub struct IterOverVecVec<'a> {
m: &'a dyn IterTrait,
}
impl<'a> Iterator for IterOverVecVec<'a> {
type Item = u16;
fn next(&mut self) -> Option {
Some(1)
}
}
impl<'a> IterOverVecVec<'a> {
fn new(m: &'a dyn…
TB_erryin
- 33
- 6
3
votes
1 answer
LifetimeScoping error in Web API self hosted app and Simple Injector
I read these (+ , + , + and +) pages, but I cannot figure out what should I do.
I have this simple interface and concrete type:
public interface IIdentifierGenerator {
long Generate(Type type);
long Generate(TType type);
}
public…
amiry jd
- 27,021
- 30
- 116
- 215
2
votes
0 answers
Rust ref mut vs .as_mut() when using inside while let Some
I'm having trouble understanding the difference in the two examples are and why the second doesn't work? I can't assign tho list.next in the second because it's borrowed as mutably.
struct List {
value: T,
next:…
Domasch
- 21
- 2
2
votes
2 answers
Lifetime specification for closure return type
I have the following snippet of code (lifetimes attempts elided):
pub struct NamedArgument(pub(in crate) &'static str, pub(in crate) T);
pub struct LoggedArgument(pub(in crate) &'static str, pub(in crate) T);
impl NamedArgument {
…
Folling
- 415
- 3
- 12
2
votes
1 answer
Converting a struct with ownership to use lifetimes and borrowed copies: no more Default?
I have a library that I'm writing that's entirely based around ownership. Mostly as an academic exercise, I'm looking at migrating it to use lifetimes. Given something like this,
#[derive(Default)]
struct Foo { test: i32 }
#[derive(Default)]
struct…
Evan Carroll
- 78,363
- 46
- 261
- 468
2
votes
1 answer
Why do Rust lifetimes matter when I move values into a spawned Tokio task?
I'm trying to create a struct that will manage a Tokio task with one tokio::sync::mpsc::Sender that sends input to the task, one tokio::sync::mpsc::Receiver that receives output from the task, and a handle that I can join at the end.
use…
John Stanford
- 993
- 1
- 7
- 18
2
votes
1 answer
Rust lifetime scoping in structs
So, I'm working on porting a string tokenizer that I wrote in Python over to Rust, and I've run into an issue I can't seem to get past with lifetimes and structs.
So, the process is basically:
Get an array of files
Convert each file to a…
dougalg
- 529
- 4
- 14
2
votes
2 answers
What is the point of an explicit lifetime for a method that doesn't take any arguments?
On page 295 of Programming Rust you can find the following:
Fortunately, the standard library includes the blanket implementation:
impl<'a, T, U> AsRef for &'a T
where
T: AsRef,
T: ?Sized,
U: ?Sized,
{
fn as_ref(&self) -> &U…
Evan Carroll
- 78,363
- 46
- 261
- 468
2
votes
2 answers
Lifetimes in generic trait implementation
I want to make a trait similar to the below structure (my particular use case is a bit more complex but this captures the issue and error I'm getting). The issue I have is which lifetimes in the last impl. I think I need to squeeze them into the…
Clinton
- 22,361
- 15
- 67
- 163
2
votes
0 answers
Accessing different fields of the same struct simultaneously and mutably
I'm trying to write a card game in Rust but ran into some trouble with the borrow checker. My main struct is the Game, which looks like this
struct Game {
players: HashMap,
deck: Vec,
}
Player is something like
struct…
red_trumpet
- 601
- 1
- 6
- 15
2
votes
1 answer
Mutable reference lives long enough when function is called directly, but doesn't live long enough when called through an intermediate function
For the following Rust code:
fn facing_of_mut<'a>(domain: &'a mut Domain, entity: Entity) -> Option<&'a mut Direction> {
component_of_mut(&mut domain, entity)
}
...the compiler outputs:
error: `domain` does not live long enough
-->…
Flaise
- 571
- 3
- 11
2
votes
1 answer
Is it possible to add registrations to an Autofac LifetimeScope after it was created?
I know that you can add registrations to a LifetimeScope when it is created like this:
using(var scope = container.BeginLifetimeScope(builder =>
{ builder.RegisterType().As();
builder.RegisterModule();
…
dmorganb
- 1,408
- 16
- 26
2
votes
2 answers
C++ Destroying Variables via Scoping
Is it safe or acceptable practice to create 'temporary' objects in C++ with an empty scope (such as the following), in order to ensure they are immediately destroyed?
{
SingularPurpose singular(&ptr_to_something);
}
Bryn McKerracher
- 683
- 6
- 21
2
votes
1 answer
Scoping of a for loop in Javascript
Consider the following code:
for (var x = 0; x < 10; x++) { /* do awesome stuff. 10 times! */ }
console.log(x);
x is still printed in the console.
This gives me warnings in JSHint, because a couple of lines further I do another loop, redeclaring…
Anemoia
- 7,928
- 7
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