I’ve found it useful to let the compiler guide me: fn to_words(text: &str) { // Note no return type text.split(‘ ‘) } Compiling gives: error[E0308]: mismatched types –> src/lib.rs:5:5 | 5 | text.split(‘ ‘) | ^^^^^^^^^^^^^^^ expected (), found struct `std::str::Split` | = note: expected type `()` found type `std::str::Split<‘_, char>` help: try adding a … Read more
The traits each represent more and more restrictive properties about closures/functions, indicated by the signatures of their call_… method, and particularly the type of self: FnOnce (self) are functions that can be called once FnMut (&mut self) are functions that can be called if they have &mut access to their environment Fn (&self) are functions … Read more
You can specify multiple binaries using [[bin]], as mentioned here: [[bin]] name = “daemon” path = “src/daemon/bin/main.rs” [[bin]] name = “client” path = “src/client/bin/main.rs” Tip: If you instead put these files in src/bin/daemon.rs and src/bin/client.rs, you’ll get two executables named daemon and client as Cargo compiles all files in src/bin into executables with the same … Read more
Clone is designed for arbitrary duplications: a Clone implementation for a type T can do arbitrarily complicated operations required to create a new T. It is a normal trait (other than being in the prelude), and so requires being used like a normal trait, with method calls, etc. The Copy trait represents values that can … Read more
To convert a slice of bytes to a string slice (assuming a UTF-8 encoding): use std::str; // // pub fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> // // Assuming buf: &[u8] // fn main() { let buf = &[0x41u8, 0x41u8, 0x42u8]; let s = match str::from_utf8(buf) { Ok(v) => v, Err(e) => panic!(“Invalid UTF-8 sequence: {}”, … Read more
TL;DR: One can instead use &str, &[T] or &T to allow for more generic code. One of the main reasons to use a String or a Vec is because they allow increasing or decreasing the capacity. However, when you accept an immutable reference, you cannot use any of those interesting methods on the Vec or … Read more
As you may have noticed, Rust does not have exceptions. It has panics, but their use for error-handling is discouraged (they are meant for unrecoverable errors). In Rust, error handling uses Result. A typical example would be: fn halves_if_even(i: i32) -> Result<i32, Error> { if i % 2 == 0 { Ok(i / 2) } … Read more
Cargo passes some metadata to the compiler through environment variables, a list of which can be found in the Cargo documentation pages. The compiler environment is populated by fill_env in Cargo’s code. This code has become more complex since earlier versions, and the entire list of variables is no longer obvious from it because it … Read more
You don’t need the mod hello in your hello.rs file. Code in any file but the crate root (main.rs for executables, lib.rs for libraries) is automatically namespaced in a module. To include the code from hello.rs in your main.rs, use mod hello;. It gets expanded to the code that is in hello.rs (exactly as you … Read more
Non-answer answer Avoid global state in general. Instead, construct the object somewhere early (perhaps in main), then pass mutable references to that object into the places that need it. This will usually make your code easier to reason about and doesn’t require as much bending over backwards. Look hard at yourself in the mirror before … Read more