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<main>
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<h1 id="struct"><a class="header" href="#struct">Struct</a></h1>
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<h3 id="the-types-of-structs"><a class="header" href="#the-types-of-structs">The types of structs</a></h3>
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<ol>
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<li>🌟 We must specify concrete values for each of the fields in struct.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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println!("Success!");
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} </code></pre></pre>
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<ol start="2">
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<li>🌟 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.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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struct Unit;
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trait SomeTrait {
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// ...Some behaviors defined here.
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}
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// We don't care about what fields are in the Unit, but we care about 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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println!("Success!");
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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: __) { }</code></pre></pre>
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<ol start="3">
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<li>🌟🌟🌟 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 to give the whole tuple a name, but don't care about the fields's names.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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println!("Success!");
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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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}</code></pre></pre>
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<h3 id="operating-on-structs"><a class="header" href="#operating-on-structs">Operating on structs</a></h3>
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<ol start="4">
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<li>🌟 You can make a whole struct mutable when instantiating it, but Rust doesn't allow us to mark only certain fields as mutable.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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 blank
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__ = String::from("sunfei");
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println!("Success!");
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}</code></pre></pre>
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<ol start="5">
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<li>🌟 Using <em>field init shorthand syntax</em> to reduce repetitions.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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println!("Success!");
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}
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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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}</code></pre></pre>
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<ol start="6">
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<li>🌟 You can create instance from other instance with <em>struct update syntax</em></li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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println!("Success!");
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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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}</code></pre></pre>
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<h3 id="print-the-structs"><a class="header" href="#print-the-structs">Print the structs</a></h3>
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<ol start="7">
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<li>🌟🌟 We can use <code>#[derive(Debug)]</code> to <a href="https://doc.rust-lang.org/book/ch05-02-example-structs.html?highlight=%23%5Bderive(Debug)%5D#adding-useful-functionality-with-derived-traits">make a struct printable</a>.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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||
|
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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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||
}</code></pre></pre>
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<h3 id="partial-move"><a class="header" href="#partial-move">Partial move</a></h3>
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<p>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.</p>
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<h4 id="example"><a class="header" href="#example">Example</a></h4>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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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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||
|
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println!("The person's name is {}", name);
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||
|
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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);
|
||
}</code></pre></pre>
|
||
<h4 id="exercises"><a class="header" href="#exercises">Exercises</a></h4>
|
||
<ol start="8">
|
||
<li>🌟🌟</li>
|
||
</ol>
|
||
<pre><pre class="playground"><code class="language-rust editable edition2021">
|
||
// Fix errors to make it work
|
||
#[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;
|
||
|
||
// ONLY modify this line
|
||
println!("{}, {}, {:?}",f.name, f.data, f);
|
||
} </code></pre></pre>
|
||
<blockquote>
|
||
<p>You can find the solutions <a href="https://github.com/sunface/rust-by-practice/blob/master/solutions/compound-types/struct.md">here</a>(under the solutions path), but only use it when you need it</p>
|
||
</blockquote>
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||
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