Hacker News Reader

Comment by beanjuiceII | Hacker News Reader

i dont think manual ser/de is common at all, and languages like dart where it was used is a massive pain point for people so much that they are adding macros to the language and the first macro they add is for serialization. whats not explicit about saying hey i have a struct this is the data i expect, serialize/deseralize in this shape, validation is a another but separate concern. in javascript you are not doing anything manually so i'm not sure why thats an example?

View on HN

I'm a bit confused. How can you control how your data is serialized if not manually? Are there languages that use some kind of magically-figures-it-out layer that negotiates the appropriate serialization on the fly?

Many languages have some kind of macro or codegen system that allows serializing or deserializing based on type definitions. Eg (pseudocode):

    @deriving(json)
    class Person:
      id: int
      name: str

Would give you something like:

    def parse(s: str): Person: ...
    def print(p: Person): str: ...

I see, thanks. I thought maybe we were talking about the choice of json vs something else being automatic and chosen at runtime.

C# (or more precisely .NET libraries) does it using reflection. Attributes let you adjust the behaviour.

Or with build-time source generation (because this specific pattern of reflection is AOT-unfriendly). It's not as convenient if you are using default serializer options, but if you don't - it ties together JsonTypeInfo<T> and JsonSerializerOptions, so it ends up being a slightly terser way to write it. I do prefer the Rust-style serde annotations however.

  record User(string Name, DateOnly DoB);

  [JsonSerializable(typeof(User))]
  partial class SerializerContext: JsonSerializerContext;

  ...
  var user = new User("John", new(1984, 1, 1));
  var response = await http.PostAsJsonAsync(
    url, user, SerializerContext.Default.User);

Sorry I wasn’t clear; I meant to use JavaScript as an example where it isn’t manual.

Despite it being easy to use, I find I inevitably wind up requiring a lot of ceremony and effort to ensure it’s safe. I’m not a huge fan of automatic serialization in that it appears to work fine when sometimes it shouldn’t/won’t. I agree that it’s a lot of effort though. I guess the question is if you want the effort up front or later on. I prefer up front, I guess.

Reply on news.ycombinator.com