• snaggen@programming.devOP
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    1 year ago

    But the author doesn’t mention the most common way to pass named argument, so I include a comment from mjec over at lobster.rs that covers that (since I’m to lazy to write my own):

    It’s not obvious to me why the author didn’t include direct instantiation of the struct, rather than a builder:

    #[derive(Default)]
    struct SearchOptions {
       pub include_inactive: bool,
       pub age_within: Option<(u32, u32)>,
       // ...
    }
    
    let result = search_users(
     users,
     SearchOptions {
       include_inactive: true,
       age_within: Some((5, 29)),
       ..Default::default()
     }
    );
    

    This avoids the need for boilerplate enums, or to filter through a vec in order to find the value of an argument. Every caller has to specify …Default::default() but I don’t mind that! I like the idea that you have to explicitly acknowledge that you want everything else to be default values (and it might be useful to omit it in some places, so you get a compile error if new options are introduced).

    • DolceTriade@programming.dev
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      1 year ago

      ya, maybe it’s the author’s ruby background? For example, in languages like go and C, using structs for optional arguments is basically the norm.

    • taladar@sh.itjust.works
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      1 year ago

      I would say the main downside of that approach is that it doesn’t give you an error for new options in the version that includes Default::default(). There might also be some issues with new options being breaking changes but I am not familiar enough with the rules for that to say.