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58 lines
1.4 KiB
Rust
58 lines
1.4 KiB
Rust
// ./src/scope/borrow/ref.md
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#[derive(Clone, Copy)]
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struct Point { x: i32, y: i32 }
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fn part0() {
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let c = 'Q';
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// A `ref` borrow on the left side of an assignment is equivalent to
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// an `&` borrow on the right side.
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let ref ref_c1 = c;
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let ref_c2 = &c;
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println!("ref_c1 equals ref_c2: {}", *ref_c1 == *ref_c2);
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let point = Point { x: 0, y: 0 };
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// `ref` is also valid when destructuring a struct.
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let _copy_of_x = {
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// `ref_to_x` is a reference to the `x` field of `point`.
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let Point { x: ref ref_to_x, y: _ } = point;
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// Return a copy of the `x` field of `point`.
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*ref_to_x
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};
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// A mutable copy of `point`
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let mut mutable_point = point;
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{
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// `ref` can be paired with `mut` to take mutable references.
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let Point { x: _, y: ref mut mut_ref_to_y } = mutable_point;
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// Mutate the `y` field of `mutable_point` via a mutable reference.
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*mut_ref_to_y = 1;
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}
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println!("point is ({}, {})", point.x, point.y);
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println!("mutable_point is ({}, {})", mutable_point.x, mutable_point.y);
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// A mutable tuple that includes a pointer
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let mut mutable_tuple = (Box::new(5u32), 3u32);
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{
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// Destructure `mutable_tuple` to change the value of `last`.
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let (_, ref mut last) = mutable_tuple;
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*last = 2u32;
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}
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println!("tuple is {:?}", mutable_tuple);
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}
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pub fn main() {
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part0();
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}
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