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<h1 id="objects"><a class="header" href="#objects">Objects</a></h1>
<blockquote>
<p><a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL objects</a> represent a list of named fields, each of which yield a value of a specific type.</p>
</blockquote>
<p>When declaring a <a href="https://graphql.org/learn/schema">GraphQL schema</a>, most of the time we deal with <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL objects</a>, because they are the only place where we actually define the behavior once <a href="https://graphql.org/learn/schema">schema</a> gets <a href="https://spec.graphql.org/October2021#sec-Execution">executed</a>.</p>
<p>There are two ways to define a <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> in <a href="https://docs.rs/juniper">Juniper</a>:</p>
<ol>
<li>The easiest way, suitable for trivial cases, is to use the <a href="https://docs.rs/juniper/0.16.1/juniper/derive.GraphQLObject.html"><code>#[derive(GraphQLObject)]</code> attribute</a> on a <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a>, as described below.</li>
<li>The other way, using the <a href="https://docs.rs/juniper/0.16.1/juniper/attr.graphql_object.html"><code>#[graphql_object]</code> attribute</a>, is described in the <a href="complex_fields.html">"Complex fields" chapter</a>.</li>
</ol>
<h2 id="trivial"><a class="header" href="#trivial">Trivial</a></h2>
<p>While any type in <a href="https://www.rust-lang.org">Rust</a> can be exposed as a <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a>, the most common one is a <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a>:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
struct Person {
name: String,
age: i32,
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<p>This creates a <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> type called <code>Person</code>, with two fields: <code>name</code> of type <code>String!</code>, and <code>age</code> of type <code>Int!</code>. Because of <a href="https://www.rust-lang.org">Rust</a>'s type system, everything is exported as <a href="https://spec.graphql.org/October2021#sec-Non-Null">non-<code>null</code></a> by default.</p>
<blockquote>
<p><strong>TIP</strong>: If a <code>null</code>able field is required, the most obvious way is to use <code>Option</code>. Or <a href="https://docs.rs/juniper/0.16.1/juniper/enum.Nullable.html"><code>Nullable</code></a> for distinguishing between <a href="https://spec.graphql.org/October2021#sel-EAFdRDHAAEJDAoBxzT">explicit and implicit <code>null</code>s</a>.</p>
</blockquote>
<h3 id="documentation"><a class="header" href="#documentation">Documentation</a></h3>
<p>We should take advantage of the fact that <a href="https://graphql.org">GraphQL</a> is <a href="https://spec.graphql.org/October2021#sec-Introspection">self-documenting</a> and add descriptions to the defined <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> type and its fields. <a href="https://docs.rs/juniper">Juniper</a> will automatically use associated <a href="https://doc.rust-lang.org/reference/comments.html#doc-comments">Rust doc comments</a> as <a href="https://spec.graphql.org/October2021#sec-Descriptions">GraphQL descriptions</a>:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>/// Information about a person.
#[derive(GraphQLObject)]
struct Person {
/// The person's full name, including both first and last names.
name: String,
/// The person's age in years, rounded down.
age: i32,
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<p>If using <a href="https://doc.rust-lang.org/reference/comments.html#doc-comments">Rust doc comments</a> is not desired (for example, when we want to keep <a href="https://www.rust-lang.org">Rust</a> API docs and GraphQL schema descriptions different), the <code>#[graphql(description = "...")]</code> attribute can be used instead, which takes precedence over <a href="https://doc.rust-lang.org/reference/comments.html#doc-comments">Rust doc comments</a>:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>/// This doc comment is visible only in Rust API docs.
#[derive(GraphQLObject)]
#[graphql(description = "This description is visible only in GraphQL schema.")]
struct Person {
/// This doc comment is visible only in Rust API docs.
#[graphql(desc = "This description is visible only in GraphQL schema.")]
// ^^^^ shortcut for a `description` argument
name: String,
/// This doc comment is visible in both Rust API docs and GraphQL schema
/// descriptions.
age: i32,
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<h3 id="renaming"><a class="header" href="#renaming">Renaming</a></h3>
<p>By default, <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a> fields are converted from <a href="https://www.rust-lang.org">Rust</a>'s standard <code>snake_case</code> naming convention into <a href="https://graphql.org">GraphQL</a>'s <code>camelCase</code> convention:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
struct Person {
first_name: String, // exposed as `firstName` in GraphQL schema
last_name: String, // exposed as `lastName` in GraphQL schema
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<p>We can override the name by using the <code>#[graphql(name = "...")]</code> attribute:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
#[graphql(name = "WebPerson")] // now exposed as `WebPerson` in GraphQL schema
struct Person {
name: String,
age: i32,
#[graphql(name = "websiteURL")]
website_url: Option&lt;String&gt;, // now exposed as `websiteURL` in GraphQL schema
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<p>Or provide a different renaming policy for all the <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a> fields:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
#[graphql(rename_all = "none")] // disables any renaming
struct Person {
name: String,
age: i32,
website_url: Option&lt;String&gt;, // exposed as `website_url` in GraphQL schema
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<blockquote>
<p><strong>TIP</strong>: Supported policies are: <code>SCREAMING_SNAKE_CASE</code>, <code>camelCase</code> and <code>none</code> (disables any renaming).</p>
</blockquote>
<h3 id="deprecation"><a class="header" href="#deprecation">Deprecation</a></h3>
<p>To <a href="https://spec.graphql.org/October2021#sec--deprecated">deprecate</a> a <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> field, either the <code>#[graphql(deprecated = "...")]</code> attribute, or <a href="https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-deprecated-attribute">Rust's <code>#[deprecated]</code> attribute</a>, should be used:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
struct Person {
name: String,
age: i32,
#[graphql(deprecated = "Please use the `name` field instead.")]
first_name: String,
#[deprecated(note = "Please use the `name` field instead.")]
last_name: String,
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<blockquote>
<p><strong>NOTE</strong>: Only <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a>/<a href="https://spec.graphql.org/October2021#sec-Interfaces">interface</a> fields and <a href="https://spec.graphql.org/October2021#sec-Enums">GraphQL enum</a> values can be <a href="https://spec.graphql.org/October2021#sec--deprecated">deprecated</a>.</p>
</blockquote>
<h3 id="ignoring"><a class="header" href="#ignoring">Ignoring</a></h3>
<p>By default, all <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a> fields are included into the generated <a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> type. To prevent inclusion of a specific field annotate it with the <code>#[graphql(ignore)]</code> attribute:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(dead_code)]
</span><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
struct Person {
name: String,
age: i32,
#[graphql(ignore)]
password_hash: String, // cannot be queried from GraphQL
#[graphql(skip)]
// ^^^^ alternative naming, up to your preference
is_banned: bool, // cannot be queried from GraphQL
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<blockquote>
<p><strong>TIP</strong>: See more available features in the API docs of the <a href="https://docs.rs/juniper/0.16.1/juniper/derive.GraphQLObject.html"><code>#[derive(GraphQLObject)]</code></a> attribute.</p>
</blockquote>
<h2 id="relationships"><a class="header" href="#relationships">Relationships</a></h2>
<p><a href="https://spec.graphql.org/October2021#sec-Objects">GraphQL object</a> fields can be of any <a href="https://graphql.org">GraphQL</a> type, except <a href="https://spec.graphql.org/October2021#sec-Input-Objects">input objects</a>.</p>
<p>Let's see what it means to build relationships between <a href="https://spec.graphql.org/October2021#sec-Objects">objects</a>:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::GraphQLObject;
</span><span class="boring">
</span>#[derive(GraphQLObject)]
struct Person {
name: String,
age: i32,
}
#[derive(GraphQLObject)]
struct House {
address: Option&lt;String&gt;, // converted into `String` (`null`able)
inhabitants: Vec&lt;Person&gt;, // converted into `[Person!]!`
}
<span class="boring">
</span><span class="boring">fn main() {}</span></code></pre></pre>
<p>Because <code>Person</code> is a valid <a href="https://graphql.org">GraphQL</a> type, we can have a <code>Vec&lt;Person&gt;</code> in a <a href="https://doc.rust-lang.org/reference/items/structs.html">struct</a>, and it'll be automatically converted into a <a href="https://spec.graphql.org/October2021#sec-List">list</a> of <a href="https://spec.graphql.org/October2021#sec-Non-Null">non-<code>null</code>able</a> <code>Person</code> <a href="https://spec.graphql.org/October2021#sec-Objects">objects</a>.</p>
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