I have used an if-else statement to create an alias to avoid code duplication but it doesn't let me access it outside the if statement. Is there a way to solve this?

On Wednesday, 5 August 2020 at 09:05:36 UTC, Flade wrote:
> I have used an if-else statement to create an alias to avoid code duplication but it doesn't let me access it outside the if statement. Is there a way to solve this?

You're probably looking for static if:

    static if (useAlias) {
        alias myAlias = getAlias!();
    }

    myAlias foo = getFoo();


What happens is a regular if statement introduces a scope, so anything declared inside it is unavailable outside. static if does not introduce a new scope, and so its contents can be accessed.

static if only works with compile-time constant conditions, but aliases are also compile-time constructs, so this should not pose a problem.

--
  Simen

On Wednesday, 5 August 2020 at 09:25:23 UTC, Simen Kjærås wrote:
> On Wednesday, 5 August 2020 at 09:05:36 UTC, Flade wrote:
>> I have used an if-else statement to create an alias to avoid code duplication but it doesn't let me access it outside the if statement. Is there a way to solve this?
>
> You're probably looking for static if:
>
>     static if (useAlias) {
>         alias myAlias = getAlias!();
>     }
>
>     myAlias foo = getFoo();
>
>
> What happens is a regular if statement introduces a scope, so anything declared inside it is unavailable outside. static if does not introduce a new scope, and so its contents can be accessed.
>
> static if only works with compile-time constant conditions, but aliases are also compile-time constructs, so this should not pose a problem.
>
> --
>   Simen

Thanks! You see it should work but the thing is. I'm using it inside a function. I'm checking for one of the function's parameter (if parameter == false) and it says that "the variable `parameter` cannot be read at compile time. Do you know if there is a way to fix this?

On Wednesday, 5 August 2020 at 09:32:58 UTC, Flade wrote:
> Thanks! You see it should work but the thing is. I'm using it inside a function. I'm checking for one of the function's parameter (if parameter == false) and it says that "the variable `parameter` cannot be read at compile time. Do you know if there is a way to fix this?

As the error message says, the value must be known at compile time. Most likely, you can simply pass it as a template parameter:

    void fun(bool parameter)(int arg1, string arg2) {
        static if (parameter) {
        }
    }

    void main() {
        fun!true(1, "foo");
        fun!false(19, "bar");
    }

--
  Simen

On Wednesday, 5 August 2020 at 09:39:47 UTC, Simen Kjærås wrote:
> On Wednesday, 5 August 2020 at 09:32:58 UTC, Flade wrote:
>> Thanks! You see it should work but the thing is. I'm using it inside a function. I'm checking for one of the function's parameter (if parameter == false) and it says that "the variable `parameter` cannot be read at compile time. Do you know if there is a way to fix this?
>
> As the error message says, the value must be known at compile time. Most likely, you can simply pass it as a template parameter:
>
>     void fun(bool parameter)(int arg1, string arg2) {
>         static if (parameter) {
>         }
>     }
>
>     void main() {
>         fun!true(1, "foo");
>         fun!false(19, "bar");
>     }
>
> --
>   Simen

Thanks man! Works as expected! Have a great day!