42 lines
1.5 KiB
Markdown
42 lines
1.5 KiB
Markdown
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# `.iter()`
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`IntoIterator` **consumes** `self` to create an iterator.
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This has its benefits: you get **owned** values from the iterator.
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For example: if you call `.into_iter()` on a `Vec<Ticket>` you'll get an iterator that returns `Ticket` values.
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That's also its downside: you can no longer use the original collection after calling `.into_iter()` on it.
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Quite often you want to iterate over a collection without consuming it, looking at **references** to the values instead.
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In the case of `Vec<Ticket>`, you'd want to iterate over `&Ticket` values.
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Most collections expose a method called `.iter()` that returns an iterator over references to the collection's elements.
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For example:
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```rust
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let numbers: Vec<u32> = vec![1, 2];
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// `n` has type `&u32` here
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for n in numbers.iter() {
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// [...]
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}
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```
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This pattern can be simplified by implementing `IntoIterator` for a **reference to the collection**.
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In our example above, that would be `&Vec<Ticket>`.
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The standard library does this, that's why the following code works:
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```rust
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let numbers: Vec<u32> = vec![1, 2];
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// `n` has type `&u32` here
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// We didn't have to call `.iter()` explicitly
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// It was enough to use `&numbers` in the `for` loop
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for n in &numbers {
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// [...]
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}
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```
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It's idiomatic to provide both options:
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- An implementation of `IntoIterator` for a reference to the collection.
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- An `.iter()` method that returns an iterator over references to the collection's elements.
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The former is convenient in `for` loops, the latter is more explicit and can be used in other contexts.
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