add solutions for struct.md

solutions/compound-types/struct.md

@@ -0,0 +1,155 @@
+1.
+```rust
+struct Person {
+    name: String,
+    age: u8,
+    hobby: String
+}
+fn main() {
+    let age = 30;
+    let p = Person {
+        name: String::from("sunface"),
+        age,
+        hobby: "coding".to_string()
+    };
+} 
+```
+
+2.
+```rust
+struct Unit;
+trait SomeTrait {
+    // ...Some behavours defines here
+}
+
+// We don't care the the fields are in Unit, but we care its behaviors.
+// So we use a struct with no fields and implement some behaviors for it
+impl SomeTrait for Unit {  }
+fn main() {
+    let u = Unit;
+    do_something_with_unit(u);
+} 
+
+// fill the blank to make the code work
+fn do_something_with_unit(u: Unit) {   }
+```
+
+3.
+```rust
+struct Color(i32, i32, i32);
+struct Point(i32, i32, i32);
+fn main() {
+    let v = Point(0, 127, 255);
+    check_color(v);
+}   
+
+fn check_color(p: Point) {
+    let Point(x, _, _) = p;
+    assert_eq!(x, 0);
+    assert_eq!(p.1, 127);
+    assert_eq!(p.2, 255);
+}
+```
+
+4.
+```rust
+struct Person {
+    name: String,
+    age: u8,
+}
+fn main() {
+    let age = 18;
+    let mut p = Person {
+        name: String::from("sunface"),
+        age,
+    };
+
+    // how can you believe sunface is only 18? 
+    p.age = 30;
+
+    p.name = String::from("sunfei");
+}
+```
+
+5.
+```rust
+struct Person {
+    name: String,
+    age: u8,
+}
+fn main() {} 
+
+fn build_person(name: String, age: u8) -> Person {
+    Person {
+        age,
+        name
+    }
+}
+```
+
+6.
+```rust
+struct User {
+    active: bool,
+    username: String,
+    email: String,
+    sign_in_count: u64,
+}
+fn main() {
+    let u1 = User {
+        email: String::from("someone@example.com"),
+        username: String::from("sunface"),
+        active: true,
+        sign_in_count: 1,
+    };
+
+    let u2 = set_email(u1);
+} 
+
+fn set_email(u: User) -> User {
+    User {
+        email: String::from("contact@im.dev"),
+        ..u
+    }
+}
+```
+
+7.
+```rust
+#[derive(Debug)]
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+fn main() {
+    let scale = 2;
+    let rect1 = Rectangle {
+        width: dbg!(30 * scale), // print debug info to stderr and assign the value of  `30 * scale` to `width`
+        height: 50,
+    };
+
+    dbg!(&rect1); // print debug info to stderr
+
+    println!("{:?}", rect1); // print debug info to stdout
+}
+```
+
+8.
+```rust
+#[derive(Debug)]
+struct File {
+    name: String,
+    data: String,
+}
+fn main() {
+    let f = File {
+        name: String::from("readme.md"),
+        data: "Rust By Practice".to_string()
+    };
+
+    let _name = f.name;
+
+    println!("{}", f.data);
+} 
+```