2018年1月31日 · What does impl mean?. As Matthieu explained, impl X means "return a concrete implementation of trait X".Without this you have the choice of returning a concrete type that implements the trait, e.g. an UpToImpl, or erasing the type by returning a Box<Generator>.

2021年1月31日 · impl Trait for Struct .. implements the trait Trait for the struct Struct. This results in the methods of the trait being available for Struct . So, even though these two syntaxes look similar, they do 2 completely different things.

2017年7月28日 · In Rust, we use an Option to represent an optionally present value. There's no need for a -1 hack. There's no need for a -1 hack. An option can be either None or Some(x) where x would be your i64 here.

2019年10月17日 · impl<'b> Game<'b> { fn match_str(&mut self, label: &'b str) { self.handlers.push(label); } } Note that I am using an entirely different lifetime name here ('b) to illustrate that the the lifetime declaration on the struct is independent of the one on the impl block. Breaking this down: impl<'b>

2019年2月3日 · Essentially, it boils down to the fact that both impl<T> MyStruct<T> and impl MyStruct<T> are valid, but mean different things. When you move new into the impl block, you should remove the superfluous type parameters, otherwise the interface of your struct will become unusable, as the following example shows:

2020年8月12日 · I really don't like monolithic implementations of the functions for a class (in C++ speak). In that language I can split things up as I like; in Rust there are strict rules about what goes in what files. I have about 2000 lines (no comments/ docs) of impl for a struct. Logically they can be broken up into different sets; functions for managing ...

Rust traits are not exactly like the interfaces in java. Here the problem is you are requiring a type T that implements PlayerTrait but you are giving 2 different types to it while creating. T must correspond to a concrete type in the end of the day.

2015年4月27日 · I've seen a question similar to this one, but no one that tells me exactly how to implement Ord for a struct. For example, the following: struct SomeNum { name: String, value: u32, } impl...

2016年8月25日 · impl<T> Double for T where T: Xed, { fn double(&self) { /* ... However , Rust has principled generics. The only thing that you know about T in the previous implementation is that T implements the Xed trait , and therefore the only associated types/functions you can use are those coming from Xed .

That means that Rust doesn't know how much space to allocate for the type. You cannot return a reference to a local variable, either, so returning &dyn Iterator is a non-starter. Impl trait. As of Rust 1.26, you can use impl trait: