建立和使用結構值

考慮以下 struct 定義：

struct Foo {
    my_bool: bool,
    my_num: isize,
    my_string: String,
}
struct Bar (bool, isize, String);
struct Baz;

為這些型別構造新的結構值非常簡單：

let foo = Foo { my_bool: true, my_num: 42, my_string: String::from("hello") };
let bar = Bar(true, 42, String::from("hello"));
let baz = Baz;

使用 . 訪問結構的欄位：

assert_eq!(foo.my_bool, true);
assert_eq!(bar.0, true); // tuple structs act like tuples

對結構的可變繫結可以使其欄位發生變異：

let mut foo = foo;
foo.my_bool = false;
let mut bar = bar;
bar.0 = false;

Rust 的模式匹配功能也可用於窺視 struct：

// creates bindings mb, mn, ms with values of corresponding fields in foo
let Foo { my_bool: mb, my_num: mn, my_string: ms } = foo;
assert_eq!(mn, 42);
// .. allows you to skip fields you do not care about
let Foo { my_num: mn, .. } = foo;
assert_eq!(mn, 42);
// leave out `: variable` to bind a variable by its field name
let Foo { my_num, .. } = foo;
assert_eq!(my_num, 42);

或者使用 Rust 的更新語法使用第二個結構作為模板建立結構 ：

let foo2 = Foo { my_string: String::from("world"), .. foo };
assert_eq!(foo2.my_num, 42);