Re: template with enum arg ?

[Ali Çehreli via Digitalmars-d-learn]

On 06/08/2016 10:02 AM, chmike wrote:

In a first implementation I defined a named enum in my class which I
could use with my template function foo.

----
final class Info {
    ...
    enum Value { info_1 = 1, ... }
    ...
    static bar(Value e) {...}
}

void foo(T)(T.Value e) { T.bar(e); }

----

I could then write : foo(Info.Value.info_1);

I would prefer to write : foo(Info.info_1);

If I change the enum into an anonymous enum the template doesn't work
anymore.

How could I solve this ?

Also, do I need a template argument filter if() ?

One way is to bring the enum values to the class scope:

    alias info_1 = Value.info_1;

Which can be automated with a mixin:

string expandEnumMembers(E)() {
    string result;

    foreach (m; __traits(allMembers, E)) {
        import std.string : format;
        result ~= format("alias %s = %s.%s;", m, E.stringof, m);
    }

    return result;
}

final class Info {
    enum Value { info_1 = 1, info_2 }

    mixin (expandEnumMembers!Value());

    static bar(Value e) {}
}

void foo(T)(T.Value e) {
    T.bar(e);
}

void main() {
    foo(Info.info_1);
    foo(Info.info_2);
}

To see at compile time what is being mixed in, insert the following 
somewhere in your code:

pragma(msg, expandEnumMembers!(Info.Value));

Ali