traits

I'm trying to implement something in Rust that works like a C++ virtual function in a class, I would have a base struct with data, then I would keep some functions undefined, like the following example: class A { int stuff; public: virtual void foo(int a, int b) = 0; void function_that_calls_foo() { /*...*/ foo(1, 2); /*...*/ } } class B: public A { void foo(int a, int b) { /* ... */ } } I was trying to implement it using function pointers, but without much success. I could use a trait with A's functions, and implement A on the other class, but I would lose the struct's data. What's the best

I have written a problem solver in Rust which as a subroutine needs to make calls to a function which is given as a black box (essentially I would like to give an argument of type Fn(f64) -> f64 ). Essentially I have a function defined as fn solve<F>(f: F) where F : Fn(f64) -> f64 { ... } which means that I can call solve like this: solve(|x| x); What I would like to do is to pass a more complex function to the solver, i.e. a function which depends on multiple parameters etc. I would like to be able to pass a struct with a suitable trait implementation to the solver. I tried the following:

Why does x.func below return "B extends B extends B" ? How to arrange this code so that it returns "B extends A extends Base" ? trait Base { def name = "Base" def func = name } trait A extends Base { override def name = "A" override def func = name + " extends " + super.func } trait B extends Base { override def name = "B" override def func = name + " extends " + super.func } val x = new Base with A with B println(x.func) Update: One arrangement could be as follows. It now has identical definitions of func1 in A and B . It does not work if I try to move it to the Derived class. Any ideas how

I am trying to write a trait which works with a database and represents something which can be stored. To do this, the trait inherits from others, which includes the serde::Deserialize trait. trait Storable<'de>: Serialize + Deserialize<'de> { fn global_id() -> &'static [u8]; fn instance_id(&self) -> Vec<u8>; } struct Example { a: u8, b: u8 } impl<'de> Storable<'de> for Example { fn global_id() -> &'static [u8] { b"p" } fn instance_id(&self) -> Vec<u8> { vec![self.a, self.b] } } Next, I am trying to write this data using a generic function: pub fn put<'de, S: Storable>(&mut self, obj: &'de S)

I need an example of where to exactly create the file, to write to it, and how to use the functions declared in the trait. I use Laravel Framework 5.4.18 -I have not altered any folder in the framework, everything is where it corresponds- From already thank you very much. I have Create a Traits directory in my Http directory with a Trait called BrandsTrait.php and use it like: use App\Http\Traits\BrandsTrait; class YourController extends Controller { use BrandsTrait; public function addProduct() { //$brands = Brand::all(); // $brands = $this->BrandsTrait(); // this is wrong $brands = $this-

It's very sad.My spark version is 2.1.1,Scala version is 2.11 import org.apache.spark.SparkContext._ import com.mufu.wcsa.component.dimension.{DimensionKey, KeyTrait} import com.mufu.wcsa.log.LogRecord import org.apache.spark.rdd.RDD object PV { // def stat[C <: LogRecord,K <:DimensionKey](statTrait: KeyTrait[C ,K],logRecords: RDD[C]): RDD[(K,Int)] = { val t = logRecords.map(record =>(statTrait.getKey(record),1)).reduceByKey((x,y) => x + y) I got this error at 1502387780429 [ERROR] /Users/lemanli/work/project/newcma/wcsa/wcsa_my/wcsavistor/src/main/scala/com/mufu/wcsa/component/stat/PV.scala

This question already has an answer here: I implemented a trait for another trait but cannot call methods from both traits 2 answers I am trying to create a base trait that will implement other operator traits ( Add , Subtract , Multiply , Divide , etc...) for me. This fails to compile, it looks like an issued with Sized , but even when Measurement is set to require Sized it does not work. Is this even possible? use std::ops::Add; #[derive(Copy, Clone, Debug)] struct Unit { value: f64, } impl Unit { fn new(value: f64) -> Unit { Unit { value: value } } } trait Measurement: Sized { fn get_value(

The following code: trait T { function foo() {} } class C { use T { T::foo as bar; } use T { T::foo as baz; } } Produces the following error: Trait method bar has not been applied, because there are collisions with other trait methods on C Is it possible to use a trait twice in a class? To "import" a method defined in a trait multiple times with different names do this: class C { use T { foo as bar; foo as baz; } } Yes, you can use a trait twice: trait T { function foo() {} } class C { use T { T::foo as bar; T::foo as baz; } } 来源： https://stackoverflow.com/questions/13582061/how-to-use-a-trait