this post was submitted on 23 Sep 2024
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Rust Programming

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Which of these code styles do you find preferable?

First option using mut with constructor in the beginning:

  let mut post_form = PostInsertForm::new(
    data.name.trim().to_string(),
    local_user_view.person.id,
    data.community_id,
  );
  post_form.url = url.map(Into::into);
  post_form.body = body;
  post_form.alt_text = data.alt_text.clone();
  post_form.nsfw = data.nsfw;
  post_form.language_id = language_id;

Second option without mut and constructor at the end:

  let post_form = PostInsertForm {
    url: url.map(Into::into),
    body,
    alt_text: data.alt_text.clone(),
    nsfw: data.nsfw,
    language_id,
    ..PostInsertForm::new(
      data.name.trim().to_string(),
      local_user_view.person.id,
      data.community_id,
    )
  };

You can see the full PR here: https://github.com/LemmyNet/lemmy/pull/5037/files

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[–] nutomic@lemmy.ml 5 points 3 weeks ago (11 children)

@DemocratPostingSucks@lemm.ee @Deebster@programming.dev @al4s@feddit.org Thanks for the feedback! Personally I prefer the first option, but based on your comments I will merge the PR with the second option.

[–] al4s@feddit.org 12 points 3 weeks ago (10 children)

If you're ever forced to do something the second way, you can also wrap it in braces, that way you end up with an immutable value again:

let app = {
  let mut app = ...
  ...
  app
};
[–] nutomic@lemmy.ml 1 points 3 weeks ago (5 children)

Thats even more verbose so the second option is better.

[–] al4s@feddit.org 6 points 3 weeks ago (1 children)

Yeah if you have the second option, use it, but if the struct has private fields it won't work.

[–] taladar@sh.itjust.works 2 points 3 weeks ago (1 children)

The first one won't work either for private fields.

[–] al4s@feddit.org 2 points 2 weeks ago (1 children)

You can have setters that set private fields, there are also sometimes structs with mixed private and public fields

[–] taladar@sh.itjust.works 1 points 2 weeks ago (1 children)

But why not use a proper builder pattern in that case?

[–] al4s@feddit.org 2 points 2 weeks ago

Because you don't control third party libraries

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