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<ol class="chapter"><li class="chapter-item expanded "><a href="motivation.html"><strong aria-hidden="true">1.</strong> Motivation</a></li><li class="chapter-item expanded "><a href="rust-basics.html"><strong aria-hidden="true">2.</strong> Rust Basics</a></li><li class="chapter-item expanded "><a href="ownership.html"><strong aria-hidden="true">3.</strong> Ownership</a></li><li class="chapter-item expanded "><a href="borrowing.html"><strong aria-hidden="true">4.</strong> Borrowing</a></li><li class="chapter-item expanded "><a href="vectors.html"><strong aria-hidden="true">5.</strong> Vectors</a></li><li class="chapter-item expanded "><a href="structs.html" class="active"><strong aria-hidden="true">6.</strong> Optional: Structures</a></li><li class="chapter-item expanded "><a href="additional_resources.html"><strong aria-hidden="true">7.</strong> Additional Resources</a></li></ol>
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<h3 id="optional-structs-in-rust"><a class="header" href="#optional-structs-in-rust">Optional: Structs in Rust</a></h3>
<h4 id="creating-a-struct"><a class="header" href="#creating-a-struct">Creating a struct</a></h4>
<p>To define a struct, we enter the keyword <code>struct</code> and name the entire struct. A struct’s name should describe the significance of the pieces of data being grouped together. Then, inside curly brackets, we define the names and types of the pieces of data, which we call <em>fields</em>. Here is an example showing a struct that stores information about a user account.</p>
<pre><pre class="playground"><code class="language-rust">
<span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>struct User {
username: String,
email: String,
sign_in_count: u64,
active: bool,
}
<span class="boring">}
</span></code></pre></pre>
<p>We create an instance by stating the name of the struct and then add curly brackets containing <code>key: value</code> pairs, where the keys are the names of the fields and the values are the data we want to store in those fields. Then we can use dot field to obtain the value in a struct.</p>
<pre><pre class="playground"><code class="language-rust">
<span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span> let mut user1 = User {
email: String::from("[email protected]"),
username: String::from("someusername123"),
active: true,
sign_in_count: 1,
};
user1.email = String::from("[email protected]");
<span class="boring">}
</span></code></pre></pre>
<p>Each fields in the struct can be referenced independently. Here's an example of defining a struct, generating an instance of it, letting it interact with functions and referencing field <code>r.h</code>.</p>
<div class="flex-container vis_block" style="position:relative; margin-left:-75px; margin-right:-75px; display: flex;">
<object type="image/svg+xml" class="struct_rect code_panel" data="assets/code_examples/struct_rect/vis_code.svg"></object>
<object type="image/svg+xml" class="struct_rect tl_panel" data="assets/code_examples/struct_rect/vis_timeline.svg" style="width: auto;" onmouseenter="helpers('struct_rect')"></object>
</div>
<h4 id="calling-a-method-in-a-struct"><a class="header" href="#calling-a-method-in-a-struct">Calling a method in a struct</a></h4>
<p>Struct can also include methods whose definition is given in the <code>impl</code> of it. When calling a method or a variable from a struct, we use <code>object.something()</code>or <code> (&object).something()</code>, which are the same. No matter it is a <code>&, &mut, *</code>or nothing, always use <code>.</code> and not need to use <code>-></code> because Rust will automatically adds in <code>&, &mut, *</code> so <code>object</code> matches the signature of the method. </p>
<div class="flex-container vis_block" style="position:relative; margin-left:-75px; margin-right:-75px; display: flex;">
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</div>
<h4 id="ownership-of-struct-data"><a class="header" href="#ownership-of-struct-data">Ownership of struct data</a></h4>
<p>When the instance of the struct owns all its fields, i.e. no reference or pointer in the struct, the ownership is basically the same with data outside of a struct. It's also possible for fields of a struct to own resources. Here's an example of the cases where one of the field <code>y</code> owns a <code>string</code> resouce.</p>
<div class="flex-container vis_block" style="position:relative; margin-left:-75px; margin-right:-75px; display: flex;">
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<p>When the any of the data members is not owned by the struct, it needs lexical lifetime specified to allow the struct owning a reference of a data resouce. This will ensure that the resource referenced will have the same lifetime as the struct as long as they share the same lexical lifetime label.</p>
<p>Here is an example of using lifetime annotations <code><'a></code> in struct definitions to allow reference of string <code>&p</code> in a <code>struct Excerpt</code>.</p>
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