self - Rust
Description: API documentation for the Rust `self` keyword in crate `std`.
Keywords: rust, rustlang, rust-lang, self

# [−]Keyword self

The receiver of a method, or the current module.

`self` is used in two situations: referencing the current module and marking the receiver of a method.

In paths, `self` can be used to refer to the current module, either in a `use` statement or in a path to access an element:

    use std::io::{self, Read};

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Is functionally the same as:

    use std::io;
    use std::io::Read;

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Using `self` to access an element in the current module:

    fn foo() {}
    fn bar() {
        self::foo()
    }

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`self` as the current receiver for a method allows to omit the parameter type most of the time. With the exception of this particularity, `self` is used much like any other parameter:

    struct Foo(i32);

    impl Foo {
        // No `self`.
        fn new() -> Self {
            Self(0)
        }

        // Consuming `self`.
        fn consume(self) -> Self {
            Self(self.0 + 1)
        }

        // Borrowing `self`.
        fn borrow(&self) -> &i32 {
            &self.0
        }

        // Borrowing `self` mutably.
        fn borrow_mut(&mut self) -> &mut i32 {
            &mut self.0
        }
    }

    // This method must be called with a `Type::` prefix.
    let foo = Foo::new();
    assert_eq!(foo.0, 0);

    // Those two calls produces the same result.
    let foo = Foo::consume(foo);
    assert_eq!(foo.0, 1);
    let foo = foo.consume();
    assert_eq!(foo.0, 2);

    // Borrowing is handled automatically with the second syntax.
    let borrow_1 = Foo::borrow(&foo);
    let borrow_2 = foo.borrow();
    assert_eq!(borrow_1, borrow_2);

    // Borrowing mutably is handled automatically too with the second syntax.
    let mut foo = Foo::new();
    *Foo::borrow_mut(&mut foo) += 1;
    assert_eq!(foo.0, 1);
    *foo.borrow_mut() += 1;
    assert_eq!(foo.0, 2);

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Note that this automatic conversion when calling `foo.method()` is not limited to the examples above. See the Reference for more information.