I thought alias could work like this with classes:

alias test = MyClass(3,"H",9.1); //Assume the constructor parameters for MyClass are (int,string,double).

Can anybody fix this code?

On 9/28/20 6:46 PM, Ruby The Roobster wrote:
> I thought alias could work like this with classes:

That would work with template parameters:

alias A = Foo!(3, "hello");

> 
> alias test = MyClass(3,"H",9.1); //Assume the constructor parameters for MyClass are (int,string,double).
> 
> Can anybody fix this code?

You have to write a function (or a lambda):

class MyClass {
  this(int, string, double) {
  }
}

auto test1() {
  return new MyClass(3,"H",9.1);
}

auto test2 = () => new MyClass(4, "I", 10.1);

void main() {
  test1();
  test2();
}

However, I assumed each invocation would create a new object. If not, something like this:

MyClass test3;
static this() {
  test3 = new MyClass(5, "J", 11.1);
}

test3 is a single instance for each thread. A single instance for the whole program would be a different exercise. :)

Ali

On Tuesday, 29 September 2020 at 01:46:56 UTC, Ruby The Roobster wrote:
> I thought alias could work like this with classes:
>
> alias test = MyClass(3,"H",9.1); //Assume the constructor parameters for MyClass are (int,string,double).
>
> Can anybody fix this code?

`alias` lets you create a new name for an entity that already exists somewhere in your program.

The "entity" in question can be a lot of different things--a type, a variable, a function, a module, a template--but it must be something that exists independently of the alias. In other words, you cannot use `alias` to give a name to something that does not already have one.

But wait, you might ask, if that's true, how can you alias a lambda? It's an anonymous function; by definition, it doesn't have a name!

    alias increment = (int x) => x + 1;

The thing is...lambdas actually do have names. They're just generated internally by the compiler. You can't actually *use* them in your code, but they do occasionally show up in error messages:

    increment("hello");
    // Error: function literal `__lambda1(int x)` is not callable using argument types `(string)`