mirror of
https://github.com/sunface/rust-by-practice.git
synced 2025-06-23 04:29:41 +00:00
add struct.md
This commit is contained in:
sunface
@ -15,7 +15,7 @@
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- [Array](compound-types/array.md)
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- [Slice](compound-types/slice.md)
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- [Tuple](compound-types/tuple.md)
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- [Struct todo](compound-types/struct.md)
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- [Struct](compound-types/struct.md)
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- [Enum todo](compound-types/enum.md)
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- [Flow Control todo](flow-control.md)
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- [Pattern Match todo](pattern-match/intro.md)
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@ -1 +1,216 @@
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# struct
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# Struct
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### There types of structs
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🌟 We must specify concrete values for each of the fields in struct.
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```rust,editable
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// fix the error
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struct Person {
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name: String,
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age: u8,
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hobby: String
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}
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fn main() {
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let age = 30;
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let p = Person {
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name: String::from("sunface"),
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age,
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};
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}
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```
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🌟 Unit struct don't have any fields. It can be useful when you need to implement a trait on some type but don’t have any data that you want to store in the type itself.
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```rust,editable
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struct Unit;
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trait SomeTrait {
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// ...Some behavours defines here
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}
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// We don't care the the fields are in Unit, but we care its behaviors.
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// So we use a struct with no fields and implement some behaviors for it
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impl SomeTrait for Unit { }
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fn main() {
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let u = Unit;
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do_something_with_unit(u);
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}
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// fill the blank to make the code work
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fn do_something_with_unit(u: __) { }
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```
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🌟🌟🌟 Tuple struct looks similar to tuples, it has added meaning the struct name provides but has no named fields. It's useful when you want give the whole tuple a name, but don't care the fields's names.
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```rust,editable
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// fix the error and fill the blanks
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struct Color(i32, i32, i32);
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struct Point(i32, i32, i32);
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fn main() {
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let v = Point(__, __, __);
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check_color(v);
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}
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fn check_color(p: Color) {
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let (x, _, _) = p;
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assert_eq!(x, 0);
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assert_eq!(p.1, 127);
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assert_eq!(__, 255);
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}
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```
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### Operate on structs
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🌟 You can make a whole struct mutable when instantiate it, but Rust doesn't allow us to mark only certain fields as mutable.
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```rust,editable
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// fill the blank and fix the error without adding/removing new line
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struct Person {
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name: String,
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age: u8,
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}
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fn main() {
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let age = 18;
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let p = Person {
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name: String::from("sunface"),
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age,
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};
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// how can you believe sunface is only 18?
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p.age = 30
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// fill the lank
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__ = String::from("sunfei");
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}
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```
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🌟 Using *field init shorthand syntax* to reduct repetitions.
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```rust,editable
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// fill the blank
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struct Person {
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name: String,
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age: u8,
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}
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fn main() {}
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fn build_person(name: String, age: u8) -> Person {
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Person {
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age,
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__
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}
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}
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```
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🌟 You can create instance from other instance with *struct update syntax*
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```rust,editable
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// fill the blank to make the code work
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struct User {
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active: bool,
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username: String,
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email: String,
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sign_in_count: u64,
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}
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fn main() {
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let u1 = User {
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email: String::from("someone@example.com"),
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username: String::from("sunface"),
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active: true,
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sign_in_count: 1,
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};
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let u2 = set_email(u1);
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}
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fn set_email(u: User) -> User {
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User {
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email: String::from("contact@im.dev"),
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__
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}
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}
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```
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### Print the structs
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🌟🌟 We can use `#[derive(Debug)]` to [make a struct prinable](https://doc.rust-lang.org/book/ch05-02-example-structs.html?highlight=%23%5Bderive(Debug)%5D#adding-useful-functionality-with-derived-traits).
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```rust,editable
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// fill the blanks to make the code work
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#[__]
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struct Rectangle {
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width: u32,
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height: u32,
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}
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fn main() {
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let scale = 2;
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let rect1 = Rectangle {
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width: dbg!(30 * scale), // print debug info to stderr and assign the value of `30 * scale` to `width`
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height: 50,
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};
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dbg!(&rect1); // print debug info to stderr
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println!(__, rect1); // print debug info to stdout
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}
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```
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### Partial move
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Within the destructuring of a single variable, both by-move and by-reference pattern bindings can be used at the same time. Doing this will result in a partial move of the variable, which means that parts of the variable will be moved while other parts stay. In such a case, the parent variable cannot be used afterwards as a whole, however the parts that are only referenced (and not moved) can still be used.
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#### Example
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```rust,editable
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fn main() {
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#[derive(Debug)]
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struct Person {
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name: String,
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age: Box<u8>,
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}
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let person = Person {
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name: String::from("Alice"),
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age: Box::new(20),
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};
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// `name` is moved out of person, but `age` is referenced
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let Person { name, ref age } = person;
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println!("The person's age is {}", age);
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println!("The person's name is {}", name);
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// Error! borrow of partially moved value: `person` partial move occurs
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//println!("The person struct is {:?}", person);
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// `person` cannot be used but `person.age` can be used as it is not moved
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println!("The person's age from person struct is {}", person.age);
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}
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```
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#### Exercises
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🌟🌟
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```rust,editable
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// fix errors to make it work
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#[derive(Debug)]
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struct File {
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name: String,
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data: String,
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}
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fn main() {
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let f = File {
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name: String::from("readme.md"),
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data: "Rust By Practice".to_string()
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};
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let _name = f.name;
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println!("{}, {}, {:?}",f.name, f.data, f);
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}
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```
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@ -15,7 +15,7 @@
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- [数组](compound-types/array.md)
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- [切片](compound-types/slice.md)
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- [元组](compound-types/tuple.md)
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- [结构体 undo](compound-types/struct.md)
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- [结构体](compound-types/struct.md)
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- [枚举 undo](compound-types/enum.md)
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- [流程控制 todo](flow-control.md)
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- [模式匹配 todo](pattern-match/intro.md)
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@ -1 +1,218 @@
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# struct
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# 结构体
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### 三种类型的结构体
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🌟 对于结构体，我们必须为其中的每一个字段都指定具体的值
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```rust,editable
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// fix the error
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struct Person {
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name: String,
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age: u8,
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hobby: String
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}
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fn main() {
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let age = 30;
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let p = Person {
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name: String::from("sunface"),
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age,
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};
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}
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```
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🌟 单元结构体没有任何字段。
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```rust,editable
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struct Unit;
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trait SomeTrait {
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// ...定义一些行为
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}
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// 我们并不关心结构体中有什么数据( 字段 )，但我们关心它的行为。
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// 因此这里我们使用没有任何字段的单元结构体，然后为它实现一些行为
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impl SomeTrait for Unit { }
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fn main() {
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let u = Unit;
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do_something_with_unit(u);
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}
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// 填空，让代码工作
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fn do_something_with_unit(u: __) { }
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```
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🌟🌟🌟 元组结构体看起来跟元组很像，但是它拥有一个结构体的名称，该名称可以赋予它一定的意义。由于它并不关心内部数据到底是什么名称，因此此时元组结构体就非常适合。
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```rust,editable
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// 填空并修复错误
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struct Color(i32, i32, i32);
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struct Point(i32, i32, i32);
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fn main() {
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let v = Point(__, __, __);
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check_color(v);
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}
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fn check_color(p: Color) {
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let (x, _, _) = p;
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assert_eq!(x, 0);
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assert_eq!(p.1, 127);
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assert_eq!(__, 255);
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}
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```
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### 结构体上的一些操作
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🌟 你可以在实例化一个结构体时将它整体标记为可变的，但是 Rust 不允许我们将结构体的某个字段专门指定为可变的.
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```rust,editable
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// 填空并修复错误，不要增加或移除代码行
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struct Person {
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name: String,
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age: u8,
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}
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fn main() {
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let age = 18;
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let p = Person {
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name: String::from("sunface"),
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age,
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};
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// how can you believe sunface is only 18?
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p.age = 30
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// 填空
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__ = String::from("sunfei");
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}
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```
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🌟 使用结构体字段初始化缩略语法可以减少一些重复代码
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```rust,editable
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// 填空
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struct Person {
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name: String,
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age: u8,
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}
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fn main() {}
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fn build_person(name: String, age: u8) -> Person {
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Person {
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age,
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__
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}
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}
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```
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🌟 你可以使用结构体更新语法基于一个结构体实例来构造另一个
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```rust,editable
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// 填空，让代码工作
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struct User {
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active: bool,
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username: String,
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email: String,
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sign_in_count: u64,
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}
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fn main() {
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let u1 = User {
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email: String::from("someone@example.com"),
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username: String::from("sunface"),
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active: true,
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sign_in_count: 1,
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};
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let u2 = set_email(u1);
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}
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fn set_email(u: User) -> User {
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User {
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email: String::from("contact@im.dev"),
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__
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}
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}
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```
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### 打印结构体
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🌟🌟 我们可以使用 `#[derive(Debug)]` 让[结构体变成可打印的](https://course.rs/basic/compound-type/struct.html#使用-derivedebug-来打印结构体的信息).
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```rust,editable
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// 填空，让代码工作
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#[__]
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struct Rectangle {
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width: u32,
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height: u32,
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}
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fn main() {
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let scale = 2;
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let rect1 = Rectangle {
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width: dbg!(30 * scale), // 打印 debug 信息到标准错误输出 stderr,并将 `30 * scale` 的值赋给 `width`
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height: 50,
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};
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dbg!(&rect1); // 打印 debug 信息到标准错误输出 stderr
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println!(__, rect1); // 打印 debug 信息到标准输出 stdout
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}
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```
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### 结构体的所有权
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当解构一个变量时，可以同时使用 `move` 和引用模式绑定的方式。当这么做时，部分 `move` 就会发生：变量中一部分的所有权被转移给其它变量，而另一部分我们获取了它的引用。
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在这种情况下，原变量将无法再被使用，但是它没有转移所有权的那一部分依然可以使用，也就是之前被引用的那部分。
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#### 示例
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```rust,editable
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fn main() {
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#[derive(Debug)]
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struct Person {
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name: String,
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age: Box<u8>,
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}
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let person = Person {
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name: String::from("Alice"),
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age: Box::new(20),
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};
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// 通过这种解构式模式匹配，person.name 的所有权被转移给新的变量 `name`
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// 但是，这里 `age` 变量确是对 person.age 的引用, 这里 ref 的使用相当于: let age = &person.age
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let Person { name, ref age } = person;
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println!("The person's age is {}", age);
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println!("The person's name is {}", name);
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// Error! 原因是 person 的一部分已经被转移了所有权，因此我们无法再使用它
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//println!("The person struct is {:?}", person);
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// 虽然 `person` 作为一个整体无法再被使用，但是 `person.age` 依然可以使用
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println!("The person's age from person struct is {}", person.age);
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}
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```
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#### 练习
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🌟🌟
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```rust,editable
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// 修复错误
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#[derive(Debug)]
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struct File {
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name: String,
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data: String,
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}
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fn main() {
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let f = File {
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name: String::from("readme.md"),
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data: "Rust By Practice".to_string()
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};
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let _name = f.name;
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println!("{}, {}, {:?}",f.name, f.data, f);
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}
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||||
```
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||||
```
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Reference in New Issue
Block a user