Rust 语言学习手册

结构体（struct）用于自定义数据类型，类似元组但字段命名。 **定义与实例化：** ```rust struct User { username: String, email: String, sign_in_count: u64, active: bool, } let user1 = User { email: String::from("someone@example.com"), username: String::from("someusername123"), active: true, sign_in_count: 1, }; ``` **可变实例：** 整体可变，不能单独字段可变。 ```rust let mut user2 = User { email: String::from("..."), ..user1 }; user2.email = String::from("new@example.com"); ``` **字段简写：** 参数名与字段名相同可简写。 ```rust fn build_user(email: String, username: String) -> User { User { email, username, active: true, sign_in_count: 1 } } ``` **元组结构体：** 类似元组，但有名。 ```rust struct Color(i32, i32, i32); let black = Color(0, 0, 0); ``` **单元结构体：** 无字段，类似空元组。 ```rust struct Unit; ```