It is easy, when declaring a class you just use the “with” keyword as often as you want class CollegeStudent extends Student with Worker with Underpaid with Young the order of the traits can be important if a trait is changing the behavior of the class, it all depends on traits you are using. Also … Read more
As you probably already know, types in Rust can be sized and unsized. Unsized types, as their name suggests, do not have a size required to store values of this type which is known to the compiler. For example, [u32] is an unsized array of u32s; because the number of elements is not specified anywhere, … Read more
Perhaps you’re expecting some kind of magic that makes type traits work. In that case, be disappointed – there is no magic. Type traits are manually defined for each type. For example, consider iterator_traits, which provides typedefs (e.g. value_type) for iterators. Using them, you can write iterator_traits<vector<int>::iterator>::value_type x; iterator_traits<int*>::value_type y; // `x` and `y` have type … Read more
As trentcl mentions, you cannot currently place impl Trait in the return position of a trait method. From RFC 1522: impl Trait may only be written within the return type of a freestanding or inherent-impl function, not in trait definitions or any non-return type position. They may also not appear in the return type of … Read more
I ended up using user sectus’s suggestion of interfaces as it feels like the least-problematic way of handling this. Using an interface to store constants rather than API contracts has a bad smell about it though so maybe this issue is more about OO design than trait implementation. interface Definition { const SOME_CONST = ‘someconst’; … Read more
You don’t have to implement Copy yourself; the compiler can derive it for you: #[derive(Copy, Clone)] enum Direction { North, East, South, West, } #[derive(Copy, Clone)] struct RoadPoint { direction: Direction, index: i32, } Note that every type that implements Copy must also implement Clone. Clone can also be derived.
I think for now the only way to do what you want is: class MyHelloWorld extends Base { use SayWorld { SayWorld::__construct as private __swConstruct; } public function __construct($a, $b, $c = 0) { $this->__swConstruct($a, $b, $c); } } Edit 2: My advice, based on over a year of dealing with traits in PHP, is: … Read more
The short answer is that you can use multiple traits — they are “stackable”. Also, traits cannot have constructor parameters. Here’s how traits are stacked. Notice that the ordering of the traits are important. They will call each other from right to left. class Ball { def properties(): List[String] = List() override def toString() = … Read more
You have trait objects when you have a pointer to a trait. Box, Arc, Rc and the reference & are all, at their core, pointers. In terms of defining a “trait object” they work in the same way. “Trait objects” are Rust’s take on dynamic dispatch. Here’s an example that I hope helps show what … Read more
You need to implement Add on &Vector rather than on Vector. impl<‘a, ‘b> Add<&’b Vector> for &’a Vector { type Output = Vector; fn add(self, other: &’b Vector) -> Vector { Vector { x: self.x + other.x, y: self.y + other.y, } } } In its definition, Add::add always takes self by value. But references … Read more