You can provide default values for your struct by implementing the Default trait. The default function would look like your current new function: impl Default for cParams { fn default() -> cParams { cParams { iInsertMax: -1, iUpdateMax: -1, iDeleteMax: -1, iInstanceMax: -1, tFirstInstance: false, tCreateTables: false, tContinue: false, } } } You can then … Read more
Let’s look at the signature for into_bytes: fn into_bytes(self) -> Vec<u8> This takes self, not a reference to self (&self). That means that self will be consumed and won’t be available after the call. In its place, you get a Vec<u8>. The prefix into_ is a common way of denoting methods like this. I don’t … Read more
If it seems that rustup did not successfully install and configure the stable toolchain, you can do it manually: rustup install stable rustup default stable After testing, it seems like my incomplete installation may have been caused by a network error. You can also try to reinstall to solve the problem.
Short answer: For maximum flexibility, you can store the callback as a boxed FnMut object, with the callback setter generic on callback type. The code for this is shown in the last example in the answer. For a more detailed explanation, read on. “Function pointers”: callbacks as fn The closest equivalent of the C++ code … Read more
These are Rust’s named lifetimes. Quoting from The Rust Programming Language: Every reference in Rust has a lifetime, which is the scope for which that reference is valid. Most of the time lifetimes are implicit and inferred, just like most of the time types are inferred. Similarly to when we have to annotate types because … Read more
extern crate foo indicates that you want to link against an external library and brings the top-level crate name into scope (equivalent to use foo). As of Rust 2018, in most cases you won’t need to use extern crate anymore because Cargo informs the compiler about what crates are present. (There are one or two … Read more
Result implements FromIterator, so you can move the Result outside and iterators will take care of the rest (including stopping iteration if an error is found). #[derive(Debug)] struct Item; type Id = String; fn find(id: &Id) -> Result<Item, String> { Err(format!(“Not found: {:?}”, id)) } fn main() { let s = |s: &str| s.to_string(); let … Read more
Updated for Rust 1.0 You cannot obtain &’static str from a String because Strings may not live for the entire life of your program, and that’s what &’static lifetime means. You can only get a slice parameterized by String own lifetime from it. To go from a String to a slice &’a str you can … Read more
The structure std::vec::Vec has method append(): fn append(&mut self, other: &mut Vec<T>) Moves all the elements of other into Self, leaving other empty. From your example, the following code will concatenate two vectors by mutating a and b: fn main() { let mut a = vec![1, 2, 3]; let mut b = vec![4, 5, 6]; … Read more
The entry API is designed for this. In manual form, it might look like let values = match map.entry(key) { Entry::Occupied(o) => o.into_mut(), Entry::Vacant(v) => v.insert(default), }; One can use the briefer form via Entry::or_insert_with: let values = map.entry(key).or_insert_with(|| default); If default is already computed, or if it’s OK/cheap to compute even when it isn’t … Read more