IT討論區(212) - 你好IT <==> 你好,IT

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https://scastie.scala-lang.org/yipZ2kMJRlGB2J9Rhu0fLg

trait Cloneable[+T <: AnyRef]:
  def test_clone(): T

case class Foo() extends Cloneable[Foo]:
  override def test_clone() = this.copy()
case class Bar()
case class Wrapper[T](value: T)

extension [T <: Cloneable[T]](x: Wrapper[T])
  def test_clone(): Wrapper[T] = Wrapper(x.value.test_clone())

def main() =
  val foo = Wrapper(Foo())
  val bar = Wrapper(Bar())

  foo.test_clone()
  bar.test_clone() // can't compile

main()

諗諗下單純係咁大部分lang都得
不過加埋polymorphism就好似幾乎得rust得

#[derive(Clone)]
struct Foo {
}

struct Bar {  
}

struct Wrapper<T> {
    pub value: T,
}

impl<T> Clone for Wrapper<T> where T : Clone {
    fn clone(&self) -> Self {
        return Wrapper {
            value: self.value.clone()
        }
    }
}

fn main() {
    let foo = Wrapper { 
        value: Foo {}
    };
    let bar = Wrapper { 
        value: Bar {}
    };
    
    clone(foo); // ok
    clone(bar); // won't compile
}

fn clone<T: Clone>(clonable: T) -> T {
    return clonable.clone()
}

C++20

萬能既c++
How?

C++本來就可以polymorphism… 隨便一個global template function clone()…

未 但對前路迷惘中

C++ concept 其實係類似structural typing ？

其實即係SAFINE既靚仔版 as in syntax易讀啲 compile error易讀啲
但係好似冇咩SAFINE做唔到既野

唔知有冇get錯
睇番你上面段code, clonable好似只係限制個object 有個clone method但冇限制具體return type
其實係咪唔type safe?
例如有個class 既clone 係return void既係咪會出事

大家都係咁過來，唔駛太驚#cn

Scala 3

係Clonable入面加個std::enable_if_t<std::is_same<T,decltype(a.clone())>::value,int>;

或者係Clonable尾加&& std::same_as<T,decltype(((T*)nullptr)->clone())>

Deploy埋過分咗
同埋應該FE,BE分開

想問microservices，做cross services data pagination, filter, search，你哋會點做？

整多個search service去aggregate data？但咁啲data唔係最update

射event出嚟，再Duplicate data，儲係要用嘅service db?

Directly call services，再人手merge埋一齊？