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RUST QUESTIONS

Consistent TypeIds for dynamically loaded crates
Consistent TypeIds for dynamically loaded crates
this one helps. After some testing I found out that the TypeIds are different because the loader crate (crate 1) is used as a library in the other 2 crates but executed as a binary.To work around the issue I extracted all of crate 1's types I wanted
TAG : rust
Date : January 12 2021, 09:11 PM , By : tanminivan
How can I require that a reference to a generic type can be compared for equality against the generic type?
How can I require that a reference to a generic type can be compared for equality against the generic type?
Any of those help You can either ignore the problem and compare a reference to a reference or non-reference to a non-reference:
TAG : rust
Date : January 12 2021, 08:33 AM , By : Pradeep Gowda
How to "use another-file" in rust? Module with hyphens in it
How to "use another-file" in rust? Module with hyphens in it
may help you . You will have to explicitly declare the module and provide its path:
TAG : rust
Date : January 12 2021, 01:40 AM , By : hellboy32
Rust generic type that can either own or borrow its content
Rust generic type that can either own or borrow its content
it helps some times std::borrow::Cow
TAG : rust
Date : January 11 2021, 05:14 PM , By : lili
Confustion with 'ref' in rust in closures
Confustion with 'ref' in rust in closures
will be helpful for those in need Taking a look at the docs page for Lines(The iterator adapter for producing lines from a str), we can see that the item produced by it is:
TAG : rust
Date : January 11 2021, 03:32 PM , By : Skee
Are all macros in the Rust std library included in the prelude?
Are all macros in the Rust std library included in the prelude?
fixed the issue. Will look into that further The standard macros are actually not in the prelude.rustc automatically adds the following code on your crate:
TAG : rust
Date : January 11 2021, 03:28 PM , By : delphiace
Why don't we need to extract values from Result in some rust iterators?
Why don't we need to extract values from Result in some rust iterators?
should help you out There are two lines in the standard library.The one on str, which returns std::str::Lines, which is an iterator of str. This is the one you are using. Splitting a string cannot fail, so it doesn't need to use Result.
TAG : rust
Date : January 11 2021, 03:26 PM , By : HokieGeek
How can I ignore extra tuple items when deserializing with Serde? ("trailing characters" error)
How can I ignore extra tuple items when deserializing with Serde? ("trailing characters" error)
I hope this helps . You can implement a custom Visitor which ignores rest of the sequence. Be aware that the whole sequence must be consumed. This is an important part (try to remove it and you'll get same error):
TAG : rust
Date : January 11 2021, 03:26 PM , By : Viv
Not comparing string in Rust
Not comparing string in Rust
Hope that helps This function will read bytes from the underlying stream until the newline delimiter (the 0xA byte) or EOF is found. Once found, all bytes up to, and including, the delimiter (if found) will be appended to buf.
TAG : rust
Date : January 09 2021, 05:38 AM , By : kangfoo2
What are best practices for `unsafe` functions in which only a small part of the code is actually doing `unsafe` things?
What are best practices for `unsafe` functions in which only a small part of the code is actually doing `unsafe` things?
hope this fix your issue If you want to use the unsafe keyword as a way to catalogue all unsafe operations, you can construct more accurate boundaries by splitting your code into safe private functions. I'm not sure if it exactly meets your requireme
TAG : rust
Date : January 08 2021, 10:52 AM , By : Kbotei
what's the best way to 'borrow' a struct deeply moved into other objects?
what's the best way to 'borrow' a struct deeply moved into other objects?
may help you . Yes, this is the only way to do it, but it is not bad at all.When you push a value into a linked list, you already moved the value's effective ownership (I said effective, because a Box only effectively owns the underlying value, but d
TAG : rust
Date : January 06 2021, 03:17 PM , By : JoeKaras
how to replace member of a structure using this member's method which consume this member itself?
how to replace member of a structure using this member's method which consume this member itself?
wish of those help You can use the take_mut crate to do that elegantly:
TAG : rust
Date : January 02 2021, 06:48 AM , By : user183526
"use of undeclared type or module" when using Diesel's `belongs_to` attribute
"use of undeclared type or module" when using Diesel's `belongs_to` attribute
hop of those help? As the error mentions, birds is not in scope. The table! macro creates a public module (birds), which you then need to bring into scope to be able to derive Associations (in models.rs):
TAG : rust
Date : January 02 2021, 06:48 AM , By : TheDave1022
Why is the width ignored for my custom formatter implementation?
Why is the width ignored for my custom formatter implementation?
seems to work fine By using write! in your fmt implementation, you are overriding the format provided by its caller.Instead you should call fmt on the strings themselves:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Steve
i need to push (Vec) of a member of struct contained, he is a struct as well
i need to push (Vec) of a member of struct contained, he is a struct as well
wish helps you I am trying to add a member of a structure that is itself a structure. I have the classic mistake "can not move out of borrowed content". , Right, so your:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Tom D
How can I invoke a Java method from Rust via JNI?
How can I invoke a Java method from Rust via JNI?
should help you out Here is a simple one-file project to demonstrate how to use the jni crate:Java side
TAG : rust
Date : January 02 2021, 06:48 AM , By : Marc Dong
Why doesn't the borrowed value live long enough when created in constructor in lifetime-annotated impl block?
Why doesn't the borrowed value live long enough when created in constructor in lifetime-annotated impl block?
should help you out I ended up using Vec as kind of linked list, so I don't have to implement my own. If you are reading this, I strongly recommend you to read Learn Rust With Entirely Too Many Linked Lists as @Jmb suggested.This solution kind of avo
TAG : rust
Date : January 02 2021, 06:48 AM , By : Tonci Grgin
Why is it impossible to dereference a boxed iterator trait object?
Why is it impossible to dereference a boxed iterator trait object?
This might help you It is impossible to move any trait object (the dyn Iterator part of your type) out from behind a pointer (dyn Iterator, Box). This is because trait objects are unsized – the compiler does not have information about the concrete si
TAG : rust
Date : January 02 2021, 06:48 AM , By : Stephen Dewar
How to build a dependency with a different version of the Rust compiler?
How to build a dependency with a different version of the Rust compiler?
To fix the issue you can do You cannot. Rust does not have a stable ABI and it is not possible to mix crates built with different versions of the compiler within the same project. As of 2019, there is no plan to stabilize the ABI.You must compile the
TAG : rust
Date : January 02 2021, 06:48 AM , By : Kbotei
How can I display a compiler warning upon function invocation?
How can I display a compiler warning upon function invocation?
like below fixes the issue The must_use seems to be fitting here and allows to specify a custom message:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Piotr Balas
How can I implement traits for type aliases?
How can I implement traits for type aliases?
this one helps. Creating a type alias does not create an entirely new type, it just allows you to refer to the existing type via a different name. Therefore, trying to implement Debug for MyFn is exactly the same as trying to implement it for Box boo
TAG : rust
Date : January 02 2021, 06:48 AM , By : sep
What order is `on_initialize` invoked across different modules in a Substrate runtime?
What order is `on_initialize` invoked across different modules in a Substrate runtime?
around this issue The on_initialize function for each Substrate runtime module is called via the Executive module, which handles all of the top-level stuff; essentially just executing blocks/extrinsics.Every time a block is executed (execute_block),
TAG : rust
Date : January 02 2021, 06:48 AM , By : CM.
Why can't I divide a BigInt with another BigInt and save it to a variable I've initialized with zero?
Why can't I divide a BigInt with another BigInt and save it to a variable I've initialized with zero?
hop of those help? I have the following code snippet: , and instead tells me that I can't divide a BigInt with a BigInt
TAG : rust
Date : January 02 2021, 06:48 AM , By : Erik
bash: gdb: No such file or directory
bash: gdb: No such file or directory
I think the issue was by ths following , From immediately below that command in the documentation you linked:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Johannes
Where will String::from("") be allocated in a match arm?
Where will String::from("") be allocated in a match arm?
I hope this helps you . Only the matching arm will be evaluated. The non matching arms have no cost apart the size of the program. In the general case, it's not even possible to evaluate other arms, as they depend on data read using destructuring of
TAG : rust
Date : January 02 2021, 06:48 AM , By : Jaya
Rustlings thread exercise, why do I NOT dereference Mutex(Struct)?
Rustlings thread exercise, why do I NOT dereference Mutex(Struct)?
To fix this issue status_shared is of type MutexGuard. MutexGuard implements the DerefMut and Deref traits, with a deref target of T (the type which is stored inside the Mutex - JobStatus in your case.When you use behind a . behind an object the rust
TAG : rust
Date : January 02 2021, 06:48 AM , By : Vinicios
Why is it not possible to update a value in a HashMap using bracket [ ] notation?
Why is it not possible to update a value in a HashMap using bracket [ ] notation?
Does that help In Rust the operators can be overloaded by the standard operator traits. The index operator (or sometimes called as subscript operator) has two flavours: Index and IndexMut. If you are looking at the documentation of the HashMap it onl
TAG : rust
Date : January 02 2021, 06:48 AM , By : Ryan Adriano
How to create a new blockchain project based on CENNZnet?
How to create a new blockchain project based on CENNZnet?
like below fixes the issue I would like to create a new blockchain project based on Substrate and integrate it with modules provided by CENNZnet such as GenericAsset and CENNZX-Spot module. , (Disclosure: I am one of the core developer of CENNZnet)
TAG : rust
Date : January 02 2021, 06:48 AM , By : user149634
How can I add 1 to a generic T?
How can I add 1 to a generic T?
Hope that helps Below is a generic type Foo. How can I correctly implement the addOne method: , You can do it with the help of the num crate:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Anthony Eden
How to group_by vector's key
How to group_by vector's key
hop of those help? I want to group a vector by key when the key is a vector. , I'm a novice at Rust and this was a challenge for me
TAG : rust
Date : January 02 2021, 06:48 AM , By : Salikh
Why doesn't Rust support overloading function or method?
Why doesn't Rust support overloading function or method?
I think the issue was by ths following , I would argue that in some way Rust does have function and method overloading.Let's say you want to implement an abs() function that can either take an integer or a floating-point number. In C++, you could use
TAG : rust
Date : January 02 2021, 06:48 AM , By : Umang
Is "this represents potential undefined behavior in your code" error when using a match arm guard a bug in the
Is "this represents potential undefined behavior in your code" error when using a match arm guard a bug in the
this one helps. This error looks like a limitation of the borrow checker to me, similar to Double mutable borrow error in a loop happens even with NLL on. I can't see how this could lead to a soundness hole, and believe the code is safe.When using an
TAG : rust
Date : January 02 2021, 06:48 AM , By : John Bentley
How to format a byte into a 2 digit hex string, in Rust
How to format a byte into a 2 digit hex string, in Rust
seems to work fine As documented in the std::fmt module:
TAG : rust
Date : January 02 2021, 06:48 AM , By : chudq7
How to store a hyper::server::Server as a field in a struct?
How to store a hyper::server::Server as a field in a struct?
will help you The problem is due to a type mismatch. In Rust, a type parameter is part of the type of a struct, so the type parameters for the server in your struct must match the ones you defined in your struct. In your case they don't. There are 2
TAG : rust
Date : January 02 2021, 06:48 AM , By : sgmichelsen
How do I modify the response body in an actix-web 1.0 middleware?
How do I modify the response body in an actix-web 1.0 middleware?
wish help you to fix your issue You can try one of these two approaches. Both of them work for me: Use map_body method from ServiceResponse:
TAG : rust
Date : January 02 2021, 06:48 AM , By : Govind Bhavan
Why does the compiler prevent me from using push on a Vec created using collect()?
Why does the compiler prevent me from using push on a Vec created using collect()?
will be helpful for those in need If you read the documentation for Vec::push and look at the signature of the method, you will learn that it does not return the Vec:
TAG : rust
Date : January 02 2021, 06:48 AM , By : user180941
Is it theoretically possible to specialise trait behaviour?
Is it theoretically possible to specialise trait behaviour?
hope this fix your issue It is possible on nightly with the still unstable specialization feature and a default implementation (see also the tracking issue for specialization):
TAG : rust
Date : January 02 2021, 06:48 AM , By : Waheedoo
How can I run a set of functions concurrently on a recurring interval without running the same function at the same time
How can I run a set of functions concurrently on a recurring interval without running the same function at the same time
like below fixes the issue You can achieve this by joining your worker futures such that they all run in parallel, but must all finish together. You can then join that with a delay of 1 second for the same rationale. Wrap that into a loop to run it f
TAG : rust
Date : January 02 2021, 06:48 AM , By : Tonci Grgin
Check if Rust is running a test build
Check if Rust is running a test build
Hope this helps I can use cfg!(debug_assertions) to check if the Rust project is running in development mode, but I'd like to know how to check if a test is being run. Is there a similar flag for tests I can use in an if statement? , You can use cfg!
TAG : rust
Date : January 02 2021, 06:48 AM , By : Eugenio
undefined reference to `printf' in Rust
undefined reference to `printf' in Rust
This might help you solved it adding rustflags = ["-C", "link-args=-lc"] to .cargo/config under the package root directory.
TAG : rust
Date : January 02 2021, 06:48 AM , By : druta
Why doesn't a move closure take ownership of a variable?
Why doesn't a move closure take ownership of a variable?
will help you The Rust Programming Language says: , The answer is given in the error message of your first example
TAG : rust
Date : January 02 2021, 06:48 AM , By : mgz
Is there any compiler flag to force undefined behavior for signed integer overflow?
Is there any compiler flag to force undefined behavior for signed integer overflow?
hop of those help? Integer overflow in Rust never triggers undefined behaviour, in contrast to C. When compiling in debug mode, arithmetic operations check for overflow and panic, but in release mode there are no checks. The behaviour can be controll
TAG : rust
Date : January 02 2021, 06:48 AM , By : 40a
Join iterator of &str
Join iterator of &str
fixed the issue. Will look into that further You could use the itertools crate for that. I use the intersperse helper in the example, it is pretty much the join equivalent for iterators.cloned() is needed to convert str items to str items, it is not
TAG : rust
Date : January 02 2021, 06:48 AM , By : demize95
Why does "move" in Rust not actually move?
Why does "move" in Rust not actually move?
To fix the issue you can do A move is a memcpy followed by treating the source as non-existent.Your big array is on the stack. That's just the way Rust's memory model works: local variables are on the stack. Since the stack space of foo is going away
TAG : rust
Date : January 02 2021, 06:48 AM , By : Gabriel
What does 0u8 mean in Rust?
What does 0u8 mean in Rust?
Hope that helps Suffixed Literals After searching, I've found this explanation in the same book:
TAG : rust
Date : January 02 2021, 06:48 AM , By : General Mills
Where does a variable passed to Reqwest's Result::read_to_string get the data from?
Where does a variable passed to Reqwest's Result::read_to_string get the data from?
wish help you to fix your issue The res object has a read_to_string() method which stores the response into the String that you pass it in
TAG : rust
Date : December 31 2020, 08:18 AM , By : evegter
How do I use tokio::timer::Timeout with Future::wait?
How do I use tokio::timer::Timeout with Future::wait?
this one helps. I wouldn't, and it's possible that you just can't.Read the documentation for the timer module:
TAG : rust
Date : December 31 2020, 08:18 AM , By : Matt Watson
Why does a variable holding the result of Vec::get_mut not need to be mutable?
Why does a variable holding the result of Vec::get_mut not need to be mutable?
hop of those help? vec.get_mut(0) returns an Option, so when you unwrap that value you will have a mutable borrow of a String. Remember, that a let statement's left side is using pattern matching, so when your pattern is just a variable name you esse
TAG : rust
Date : December 31 2020, 04:56 AM , By : Adam May
How can I use serde to serialize a struct to another Rust data structure?
How can I use serde to serialize a struct to another Rust data structure?
Hope that helps The simplest way to do this would be to use serde_json::from_value (applicable even if you're not using JSON, but requires all fields to be valid JSON [e.g. no non-string keys in hashmaps]):
TAG : rust
Date : December 28 2020, 05:45 AM , By : FriendL
Serializing a sequence in Serde when both sequence length and types must be known?
Serializing a sequence in Serde when both sequence length and types must be known?
This might help you Solved using the suggestion from mcarton about storing elements in the sequence serializer.This stores each serialized sequence of bytes in a Vec (i.e. as a Vec), and checks whether all items are of equal length before serializing
TAG : rust
Date : December 27 2020, 04:51 PM , By : user112141
How can I support an unknown or other value for a Serde enum?
How can I support an unknown or other value for a Serde enum?
Hope that helps I have a JSON API that returns an object that looks like this: , Simple case should be fine with this:
TAG : rust
Date : December 27 2020, 04:28 PM , By : 小和尚
How do I use combinators to avoid verbose matching without getting the error "cannot return value referencing funct
How do I use combinators to avoid verbose matching without getting the error "cannot return value referencing funct
wish help you to fix your issue as_ref() doesn't solve the problem because and_then() is design to consume the value, not to borrow it. As you can see, Remote borrow self and url() too.I strongly recommend you to just use ?:
TAG : rust
Date : December 27 2020, 04:18 PM , By : Nathan Good
Will the non-lexical lifetime borrow checker release locks prematurely?
Will the non-lexical lifetime borrow checker release locks prematurely?
may help you . There is a misunderstanding here: NLL (non-lexical lifetimes) affects the borrow-checks, not the actual lifetime of the objects.Rust uses RAII1 extensively, and thus the Drop implementation of a number of objects, such as locks, has si
TAG : rust
Date : December 27 2020, 04:18 PM , By : Vijayant Singh
Modify a struct while iterating over an Iterable in the struct
Modify a struct while iterating over an Iterable in the struct
Hope that helps Why? Because self.primes borrowed immutably (because of Vec::iter, i.e. the newly created iterator, Iter is referencing the vector which is owned by self) and while this is happening mark_multiples tries to borrow self as mutable. The
TAG : rust
Date : December 27 2020, 03:09 PM , By : µilad
Does a generic lifetime materialize as the reference's lifetime or the referenced value's lifetime?
Does a generic lifetime materialize as the reference's lifetime or the referenced value's lifetime?
wish of those help A value has a lifetime of its own, but a reference also tracks the lifetime of the thing it references. Unfortunately, there's a lack of official terminology to use here. The term that I (and some others) have started using is conc
TAG : rust
Date : December 26 2020, 03:01 AM , By : Bas
How do I append to a tuple?
How do I append to a tuple?
help you fix your problem There's no built-in way to do this, but we can implement it ourselves with a helper trait and a macro to implement that trait for tuples up to N arguments:
TAG : rust
Date : December 26 2020, 02:30 AM , By : user87752
What happens to heap allocated value after variable that holds the ownership of that value gets reassigned?
What happens to heap allocated value after variable that holds the ownership of that value gets reassigned?
around this issue Whenever you assign a new value to a variable of a type implementing Drop, the old value will be dropped before the new value is assigned. For a type owning heap-allocated memory like Box, this means the memory will be freed at the
TAG : rust
Date : December 26 2020, 12:30 AM , By : FarmerDave
Is `cargo clippy` a superset of `cargo check`?
Is `cargo clippy` a superset of `cargo check`?
may help you . clippy itselfs runs cargo check.
TAG : rust
Date : December 26 2020, 12:01 AM , By : onurtopcu
Injecting dynamic lib into a thread
Injecting dynamic lib into a thread
wish of those help The shared libraries are loaded into a process. It shouldn't matter what thread you've used to load the library, the code should equally be available to all the threads once the library has been loaded. This is because the POSIX th
TAG : rust
Date : December 25 2020, 10:30 PM , By : jonagh
Mutex can deference struct's but not primitives
Mutex can deference struct's but not primitives
Hope this helps c_int is not actually the integer or Counter instance, it's a std::sync::MutexGuard
TAG : rust
Date : December 25 2020, 09:01 PM , By : francisco santos

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