traits

Why do I get the error below? How to workaround it? I assumed that since A and B compile to (interface,class) pairs, it's a matter of choosing the right static method call to implement when compiling C. I would expect the priority to be according to order. scala> trait A { def hi = println("A") } defined trait A scala> trait B { def hi = println("B") } defined trait B scala> class C extends B with A <console>:6: error: error overriding method hi in trait B of type => Unit; method hi in trait A of type => Unit needs `override' modifier class C extends B with A scala> trait A { override def hi =

I have the following two functions: pub fn get_most_recent_eth_entry(conn: &SqliteConnection) -> Result<i32, Error> { let res = types::ethereum::table .order(types::ethereum::time.desc()) .limit(1) .load::<types::ETHRecord>(&*conn); match res { Ok(x) => { if x.len() > 0 { Ok(x.get(0).unwrap().time) } else { Ok(0) } } Err(err) => Err(format_err!("Error here! {:?}", err)), } } pub fn get_most_recent_btc_entry(conn: &SqliteConnection) -> Result<i32, Error> { let res = types::bitcoin::table .order(types::bitcoin::time.desc()) .limit(1) .load::<types::BTCRecord>(&*conn); match res { Ok(x) => { if x

I'm coming up with View (HTML markup) and Utility (JavaScript - behavior) architecture and creating atomic classes for composing views and utilities using ES6 Class. There will be a need that multiple utility classes can be composed/mixed into a single view class. How can ES6 Class API provide a way to mix-in class(es) into another/main class. I've looked at Object.assign but that is for objects and not at class-level. JavaScript classes right now and hopefully also in future only can be extended from each other but can not be mixed into one another. If at all, then most probably Lightweight

I'm trying to use generics but I don't master that topic well enough and I get this error: error: mismatched types: expected `book::mdbook::MDBook<R>`, found `book::mdbook::MDBook<renderer::html_handlebars::HtmlHandlebars>` (expected type parameter, found struct `renderer::html_handlebars::HtmlHandlebars`) [E0308] This is the relevant code pub struct MDBook<R> where R: Renderer { title: String, author: String, config: BookConfig, pub content: Vec<BookItem>, renderer: R, } impl<R> MDBook<R> where R: Renderer { pub fn new(path: &PathBuf) -> Self { MDBook { title: String::from(""), author: String

I've come across an odd type inference problem that has me scratching my head a bit. I'm implementing a generic trait on a struct for multiple types. I started with &str : struct Bar<'a> { baz: &'a str, } trait Foo<T> { fn foo(&self) -> T; } impl<'a> Foo<&'a str> for Bar<'a> { fn foo(&self) -> &'a str { self.baz } } #[cfg(test)] mod tests { use super::*; #[test] fn test_str_a() { let bar = Bar { baz: "asd" }; assert_eq!("asd", bar.foo()); } } This works — the problem comes when I add another implementation for the u8 type: struct Bar<'a> { baz: &'a str, } trait Foo<T> { fn foo(&self) -> T; }

I'm very new to Rust so I may have terminology confused. I want to use the hashes crates to do some hashing and I want to dynamically pick which algorithm (sha256, sha512, etc.) to use at runtime. I'd like to write something like this: let hasher = match "one of the algorithms" { "sha256" => Box::new(Sha256::new()) as Box<Digest>, "sha512" => Box::new(Sha512::new()) as Box<Digest> // etc... }; I sort of get that that doesn't work because the associated types required by Digest aren't specified. If I attempt to fill them in: "sha256" => Box::new(Sha256::new()) as Box<Digest<<OutputSize = U32,

Here is an offending example: // Some traits trait Behaviour { type Sub: SubBehaviour; } trait SubBehaviour {} // Some implementations of these traits struct A; impl Behaviour for A { type Sub = B; } struct B; impl SubBehaviour for B {} // Struct that holds a collection of these traits. struct Example<'a> { behaviours: Vec<&'a Behaviour>, } impl<'a> Example<'a> { fn add_behaviour<T: Behaviour>(&mut self, b: &'a T) { self.behaviours.push(b); } } fn main() { let b = A; let mut e = Example { behaviours: Vec::new(), }; e.add_behaviour(&b); } Playground I am getting: error[E0191]: the value of the