new idiom: Default trait #48
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idioms/default.md
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| fn interestingness(i: &Interesting) -> usize { | ||
| if really { |
idioms/default.md
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| ## Description | ||
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| Many types in Rust have a [Constructor]. However, this is *specific* to the |
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Nit: "constructor" should be lowercase here, at least.
I'm not sure if the Constructor pattern should be capitalized or not, but AFAIK when we talk about a constructor function it is always in lowercase.
idioms/default.md
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| ```rust | ||
| // note that we can simply auto-derive Default here. | ||
| #[derive(Default)] | ||
| struct Interesting { |
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Default is often used for configuration structs -- I'd prefer if we use a more configuration-like theme for the example.
idioms/default.md
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| type; Rust cannot abstract over "everything that has a `new()` method". To | ||
| allow this, the [`Default`] trait was conceived, which can be used with | ||
| containers and other generic types (e.g. see [`Option::unwrap_or_default()`]). | ||
| Notably, some containers already implement it where applicable. |
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Worth noting, though probably further down, is that new and default do different things - new typically takes values for all or most fields (i.e., is shorthand for the literal, modulo private fields), whereas default takes no arguments and thus creates an object 'from nothing'.
idioms/default.md
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| } | ||
| } | ||
| ``` | ||
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Another detail worth elaborating on is when Default can be derived, vs when it must be manually implemented.
idioms/default.md
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| not be "default" | ||
| - The [`Default`] documentation (scroll down for the list of implementors) | ||
| - [`Option::unwrap_or_default()`] | ||
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shameless plug for derive(new) - https://crates.io/crates/derive-new/
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Should this PR be merged still? Can we take the last paragraph of |
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I don't think I ever saw the new commits, sorry. |
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No need to be sorry, I've been swamped with work recently, too. |
Please review. Thank you!