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<h1 id="struct"><a class="header" href="#struct">Struct</a></h1>
<h3 id="the-types-of-structs"><a class="header" href="#the-types-of-structs">The types of structs</a></h3>
<ol>
<li>🌟 We must specify concrete values for each of the fields in struct.</li>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fix the error
struct Person {
name: String,
age: u8,
hobby: String
}
fn main() {
let age = 30;
let p = Person {
name: String::from("sunface"),
age,
};
println!("Success!");
} </code></pre></pre>
<ol start="2">
<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>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
struct Unit;
trait SomeTrait {
// ...Some behaviors defined here.
}
// We don't care about what fields are in the Unit, but we care about 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);
println!("Success!");
}
// Fill the blank to make the code work
fn do_something_with_unit(u: __) { }</code></pre></pre>
<ol start="3">
<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>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fix the error and fill the blanks
struct Color(i32, i32, i32);
struct Point(i32, i32, i32);
fn main() {
let v = Point(__, __, __);
check_color(v);
println!("Success!");
}
fn check_color(p: Color) {
let (x, _, _) = p;
assert_eq!(x, 0);
assert_eq!(p.1, 127);
assert_eq!(__, 255);
}</code></pre></pre>
<h3 id="operating-on-structs"><a class="header" href="#operating-on-structs">Operating on structs</a></h3>
<ol start="4">
<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>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fill the blank and fix the error without adding/removing new line
struct Person {
name: String,
age: u8,
}
fn main() {
let age = 18;
let p = Person {
name: String::from("sunface"),
age,
};
// How can you believe sunface is only 18?
p.age = 30;
// Fill the blank
__ = String::from("sunfei");
println!("Success!");
}</code></pre></pre>
<ol start="5">
<li>🌟 Using <em>field init shorthand syntax</em> to reduce repetitions.</li>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fill the blank
struct Person {
name: String,
age: u8,
}
fn main() {
println!("Success!");
}
fn build_person(name: String, age: u8) -&gt; Person {
Person {
age,
__
}
}</code></pre></pre>
<ol start="6">
<li>🌟 You can create instance from other instance with <em>struct update syntax</em></li>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fill the blank to make the code work
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);
println!("Success!");
}
fn set_email(u: User) -&gt; User {
User {
email: String::from("contact@im.dev"),
__
}
}</code></pre></pre>
<h3 id="print-the-structs"><a class="header" href="#print-the-structs">Print the structs</a></h3>
<ol start="7">
<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>
</ol>
<pre><pre class="playground"><code class="language-rust editable edition2021">
// Fill the blanks to make the code work
#[__]
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!(&amp;rect1); // Print debug info to stderr
println!(__, rect1); // Print debug info to stdout
}</code></pre></pre>
<h3 id="partial-move"><a class="header" href="#partial-move">Partial move</a></h3>
<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>
<h4 id="example"><a class="header" href="#example">Example</a></h4>
<pre><pre class="playground"><code class="language-rust editable edition2021">
fn main() {
#[derive(Debug)]
struct Person {
name: String,
age: Box&lt;u8&gt;,
}
let person = Person {
name: String::from("Alice"),
age: Box::new(20),
};
// `name` is moved out of person, but `age` is referenced
let Person { name, ref age } = person;
println!("The person's age is {}", age);
println!("The person's name is {}", name);
// Error! borrow of partially moved value: `person` partial move occurs
//println!("The person struct is {:?}", person);
// `person` cannot be used but `person.age` can be used as it is not moved
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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