Half-compile-time attribute extractor.

gistfile1.cpp

mixin template UriBasedRequest(T) {
    public string uri() @property const {
        UriBuilder builder = new UriBuilder();

        string[] paths;
        foreach (memberName; __traits(allMembers, T)) {
            // TODO: Iterate only over fields.
            alias Member = TypeTuple!(__traits(getMember, this, memberName))[0];
            alias MemberType = typeof(Member);
            alias Attributes = TypeTuple!(__traits(getAttributes, Member));
            static if (Attributes.length > 0) {
                static if (hasAttribute!(Member, PathAttribute)) {
                    static if (isArray!(MemberType)) {
                        // aggregate
                        // assign
                    } else static if (is(Unqual!(MemberType) : string)) {
                        string value = to!string(Member);
                        if (value.length == 0) {
                            static if (hasAttribute!(Member, QueryAttribute)) {
                                paths ~= getAttribute!(Member, DefaultAttribute).value;
                            }
                        } else {
                            paths ~= value;
                        }
                    }/+ else static if (isNullable!(typeof(Member))) {
                        if (value.isNull) {
                            static if (hasAttribute!(Member, QueryAttribute)) {
                                paths ~= getAttribute!(Member, DefaultAttribute).value;
                            }
                        } else {
                            paths ~= value;
                        }
                    }+/
                } else static if (hasAttribute!(Member, QueryAttribute)) {
                    enum name = getAttribute!(Member, QueryAttribute).name;
                    static if (name.length == 0) {
                        enum queryName = memberName;
                    } else {
                        enum queryName = name;
                    }
                    alias queryValue = Member;
                    builder.addParameter(queryName, queryValue);
                }
            }
        }

        builder.setPath(paths);
        (cast(const T)(this)).buildUri(builder);
        return builder.uri;
    }
}