new idiom: mem::replace #31
Conversation
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| ## Advantages | ||
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| Look ma, no allocation! Also you may feel like Indiana Jones while doing it. |
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I still remember the day I learned mem::replace, and this is exactly how I felt. 😎
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Welcome to the club... 😎
| // we could just take a reference to `name` and clone that, but why pay an | ||
| // extra allocation for something we already have? | ||
| let have_name = match *e { | ||
| MyEnum::A(ref mut name, x) if x == 0 => { |
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MyEnum::A{ ref mut name, x } I believe.
| _ => None | ||
| }; | ||
| // the mutable borrow ends here, so we can change `e` | ||
| if let Some(name) = have_name { *e = MyEnum::B { name } } |
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MyEnum::B { name: name } at least until the field init shorthand RFC stabilizes if accepted.
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True that. I appear to live in the future from time to time.
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Indeed, this can be quite useful. I like the example a lot. Do you mind adding a link to the table of contents? I can add a note to the clone to satisfy the borrow checker PR, or a new GH issue to remind us to update the relevant links here when that anti-pattern is finished. |
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@cbreeden that'd be great. |
This is something I recently found to be quite useful.