Proposal: user defined attributes

[Andrej Mitrovic]

On 3/19/12, Jacob Carlborg <doob at me.com> wrote:
> Yeah, but that will complicate the retrieval of the information.

What is so complicated about extracting fields? Just iterate via .tupleof:

module test;

import std.stdio;
import std.conv;

struct Foo
{
    int x;
    string name;
    mixin NonSerialized!name;
    string lastName;
    mixin NonSerialized!lastName;
    string extra;
}

mixin template NonSerialized(alias field)
{
    mixin("enum __attribute_nonSerialized_" ~ field.mangleof ~ ";");
}

string serialize(T)(T input)
{
    string result;

    foreach (i, field; input.tupleof)
    {
        static if (skipSerialize!(T, input.tupleof[i].mangleof))
            result ~= to!string(typeof(field).init) ~ "\n";
        else
            result ~= to!string(field) ~ "\n";
    }

    return result;
}

template skipSerialize(T, string mangle)
{
	enum bool skipSerialize = __traits(hasMember, T,
"__attribute_nonSerialized_" ~ mangle);
}

void main()
{
    Foo foo = Foo(10, "Foo", "Bar", "Doo");
    string bin = serialize(foo);
    writeln(bin);
}

And by using .init instead of just skipping serialization altogether
you can unserialize at a later point even if you end up removing some
of the mixins, so you can have some binary-compatibility there.