Why does ServiceStack's New API promote an "object" return type rather than something more strongly typed?

Question

For example, if I have standard request and response DTOs, linked up via IReturn<T>, what are the reasons to have a service method signature like the following, as seen in various online examples (such as this one, although not consistently throughout):

public object Get(DTO.MyRequest request)

rather than:

public IList<DTO.MyResponse> Get(DTO.MyRequest request)

Is an object return type here simply to support service features like gzip compression of the output stream, which results in the output being a byte array? It seems that one would want to have the appropriate stronger return type from these so-called "action" calls, unless I'm missing some common scenario or use case.

Answer 1

It used to be a limitation that the New API only supported an object return type, but that hasn't been the case for a while where all examples on the New API wiki page now use strong-typed responses.

One of the reasons where you might want to return an object return type is if you want to decorate the response inside a HttpResult, e.g:

    public object Post(Movie movie)
    {
        var isNew = movie.Id == null;
        Db.Save(movie); //Inserts or Updates

        var movie = new MovieResponse {
            Movie = Db.Id<Movie>(newMovieId),
        };
        if (!isNew) return movie;

        //Decorate the response if it was created
        return new HttpResult(movie) {
            StatusCode = HttpStatusCode.Created,
            Headers = {
              { HttpHeaders.Location, Request.AbsoluteUri.CombineWith(movieId) }
            }
        };
    }

It's also useful if you want to return different responses based on the request (though it's not something I recommend), e.g:

    public object Get(FindMovies request)
    {
        if (request.Id != null)
            return Db.Id<Movie>(movie.Id);

        return Db.Select<Movie>();
    }

If you do choose to return an object I highly recommend decorating your Request DTO with the IReturn<T> marker to give a hint to ServiceStack what the expected response of the service should be.