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<ol class="chapter"><li class="chapter-item expanded "><a href="../index.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="../quickstart.html"><strong aria-hidden="true">2.</strong> Quickstart</a></li><li class="chapter-item expanded "><a href="../types/index.html"><strong aria-hidden="true">3.</strong> Type System</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/objects/defining_objects.html"><strong aria-hidden="true">3.1.</strong> Defining objects</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/objects/complex_fields.html"><strong aria-hidden="true">3.1.1.</strong> Complex fields</a></li><li class="chapter-item expanded "><a href="../types/objects/using_contexts.html"><strong aria-hidden="true">3.1.2.</strong> Using contexts</a></li><li class="chapter-item expanded "><a href="../types/objects/error_handling.html"><strong aria-hidden="true">3.1.3.</strong> Error handling</a></li></ol></li><li class="chapter-item expanded "><a href="../types/other-index.html"><strong aria-hidden="true">3.2.</strong> Other types</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/enums.html"><strong aria-hidden="true">3.2.1.</strong> Enums</a></li><li class="chapter-item expanded "><a href="../types/interfaces.html"><strong aria-hidden="true">3.2.2.</strong> Interfaces</a></li><li class="chapter-item expanded "><a href="../types/input_objects.html"><strong aria-hidden="true">3.2.3.</strong> Input objects</a></li><li class="chapter-item expanded "><a href="../types/scalars.html" class="active"><strong aria-hidden="true">3.2.4.</strong> Scalars</a></li><li class="chapter-item expanded "><a href="../types/unions.html"><strong aria-hidden="true">3.2.5.</strong> Unions</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="../schema/schemas_and_mutations.html"><strong aria-hidden="true">4.</strong> Schemas and mutations</a></li><li class="chapter-item expanded "><a href="../servers/index.html"><strong aria-hidden="true">5.</strong> Adding A Server</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../servers/official.html"><strong aria-hidden="true">5.1.</strong> Official Server Integrations</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../servers/warp.html"><strong aria-hidden="true">5.1.1.</strong> Warp</a></li><li class="chapter-item expanded "><a href="../servers/rocket.html"><strong aria-hidden="true">5.1.2.</strong> Rocket</a></li><li class="chapter-item expanded "><a href="../servers/iron.html"><strong aria-hidden="true">5.1.3.</strong> Iron</a></li><li class="chapter-item expanded "><a href="../servers/hyper.html"><strong aria-hidden="true">5.1.4.</strong> Hyper</a></li></ol></li><li class="chapter-item expanded "><a href="../servers/third-party.html"><strong aria-hidden="true">5.2.</strong> Third Party Integrations</a></li></ol></li><li class="chapter-item expanded "><a href="../advanced/index.html"><strong aria-hidden="true">6.</strong> Advanced Topics</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../advanced/introspection.html"><strong aria-hidden="true">6.1.</strong> Introspection</a></li><li class="chapter-item expanded "><a href="../advanced/non_struct_objects.html"><strong aria-hidden="true">6.2.</strong> Non-struct objects</a></li><li class="chapter-item expanded "><a href="../advanced/implicit_and_explicit_null.html"><strong aria-hidden="true">6.3.</strong> Implicit and explicit null</a></li><li class="chapter-item expanded "><a href="../advanced/objects_and_generics.html"><strong aria-hidden="true">6.4.</strong> Objects and generics</a></li><li class="chapter-item expanded "><a href="../advanced/multiple_ops_per_request.html"><strong aria-hidden="true">6.5.</strong> Multiple operations per request</a></li><li class="chapter-item expanded "><a href="../advanced/dataloaders.html"><strong aria-hidden="true">6.6.</strong> Dataloaders</a></li><li class="chapter-item expanded "><a href="../advanced/subscriptions.html"><strong aria-hidden="true">6.7.</strong> Subscriptions</a></li></ol></li></ol>
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<h1 class="menu-title">Juniper Book (GraphQL server for Rust)</h1>
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<main>
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<h1 id="scalars"><a class="header" href="#scalars">Scalars</a></h1>
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<p>Scalars are the primitive types at the leaves of a GraphQL query: numbers,
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strings, and booleans. You can create custom scalars to other primitive values,
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but this often requires coordination with the client library intended to consume
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the API you're building.</p>
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<p>Since any value going over the wire is eventually transformed into JSON, you're
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also limited in the data types you can use.</p>
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<p>There are two ways to define custom scalars.</p>
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<ul>
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<li>For simple scalars that just wrap a primitive type, you can use the newtype pattern with
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a custom derive.</li>
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<li>For more advanced use cases with custom validation, you can use
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the <code>graphql_scalar</code> proc macro.</li>
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</ul>
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<h2 id="built-in-scalars"><a class="header" href="#built-in-scalars">Built-in scalars</a></h2>
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<p>Juniper has built-in support for:</p>
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<ul>
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<li><code>i32</code> as <code>Int</code></li>
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<li><code>f64</code> as <code>Float</code></li>
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<li><code>String</code> and <code>&str</code> as <code>String</code></li>
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<li><code>bool</code> as <code>Boolean</code></li>
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<li><code>juniper::ID</code> as <code>ID</code>. This type is defined <a href="https://spec.graphql.org/October2021#sec-ID">in the
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spec</a> as a type that is serialized
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as a string but can be parsed from both a string and an integer.</li>
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</ul>
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<p>Note that there is no built-in support for <code>i64</code>/<code>u64</code>, as the GraphQL spec <a href="https://spec.graphql.org/October2021#sec-Int">doesn't define any built-in scalars for <code>i64</code>/<code>u64</code> by default</a>. You may wish to leverage a <a href="#custom-scalars">custom GraphQL scalar</a> in your schema to support them.</p>
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<p><strong>Third party types</strong>:</p>
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<p>Juniper has built-in support for a few additional types from common third party
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crates. They are enabled via features that are on by default.</p>
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<ul>
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<li>uuid::Uuid</li>
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<li>chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime}</li>
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<li>chrono_tz::Tz;</li>
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<li>time::{Date, OffsetDateTime, PrimitiveDateTime, Time, UtcOffset}</li>
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<li>url::Url</li>
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<li>bson::oid::ObjectId</li>
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</ul>
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<h2 id="custom-scalars"><a class="header" href="#custom-scalars">Custom scalars</a></h2>
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<h3 id="graphqltransparent-attribute"><a class="header" href="#graphqltransparent-attribute"><code>#[graphql(transparent)]</code> attribute</a></h3>
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<p>Often, you might need a custom scalar that just wraps an existing type.</p>
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<p>This can be done with the newtype pattern and a custom derive, similar to how
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serde supports this pattern with <code>#[serde(transparent)]</code>.</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
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</span><span class="boring">
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</span>#[derive(juniper::GraphQLScalar)]
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#[graphql(transparent)]
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pub struct UserId(i32);
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#[derive(juniper::GraphQLObject)]
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struct User {
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id: UserId,
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}
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<span class="boring">
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</span><span class="boring">fn main() {}</span></code></pre></pre>
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<p><code>#[derive(GraphQLScalar)]</code> is mostly interchangeable with <code>#[graphql_scalar]</code>
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attribute:</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
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</span><span class="boring">use juniper::graphql_scalar;
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</span><span class="boring">
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</span>#[graphql_scalar(transparent)]
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pub struct UserId {
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value: i32,
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}
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#[derive(juniper::GraphQLObject)]
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struct User {
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id: UserId,
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}
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<span class="boring">
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</span><span class="boring">fn main() {}</span></code></pre></pre>
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<p>That's it, you can now use <code>UserId</code> in your schema.</p>
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<p>The macro also allows for more customization:</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
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</span>/// You can use a doc comment to specify a description.
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#[derive(juniper::GraphQLScalar)]
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#[graphql(
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transparent,
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// Overwrite the GraphQL type name.
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name = "MyUserId",
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// Specify a custom description.
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// A description in the attribute will overwrite a doc comment.
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description = "My user id description",
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)]
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pub struct UserId(i32);
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<span class="boring">
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</span><span class="boring">fn main() {}</span></code></pre></pre>
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<p>All the methods used from newtype's field can be replaced with attributes:</p>
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<h3 id="graphqlto_output_with--fn-attribute"><a class="header" href="#graphqlto_output_with--fn-attribute"><code>#[graphql(to_output_with = <fn>)]</code> attribute</a></h3>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
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</span><span class="boring">use juniper::{GraphQLScalar, ScalarValue, Value};
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</span><span class="boring">
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</span>#[derive(GraphQLScalar)]
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#[graphql(to_output_with = to_output, transparent)]
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struct Incremented(i32);
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/// Increments [`Incremented`] before converting into a [`Value`].
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fn to_output<S: ScalarValue>(v: &Incremented) -> Value<S> {
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Value::from(v.0 + 1)
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}
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<span class="boring">
|
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</span><span class="boring">fn main() {}</span></code></pre></pre>
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|
<h3 id="graphqlfrom_input_with--fn-attribute"><a class="header" href="#graphqlfrom_input_with--fn-attribute"><code>#[graphql(from_input_with = <fn>)]</code> attribute</a></h3>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
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|
</span><span class="boring">use juniper::{GraphQLScalar, InputValue, ScalarValue};
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|
</span><span class="boring">
|
|
</span>#[derive(GraphQLScalar)]
|
|
#[graphql(from_input_with = Self::from_input, transparent)]
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|
struct UserId(String);
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|
|
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impl UserId {
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|
/// Checks whether [`InputValue`] is `String` beginning with `id: ` and
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|
/// strips it.
|
|
fn from_input<S>(input: &InputValue<S>) -> Result<Self, String>
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|
where
|
|
S: ScalarValue
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|
{
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input.as_string_value()
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.ok_or_else(|| format!("Expected `String`, found: {input}"))
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.and_then(|str| {
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str.strip_prefix("id: ")
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.ok_or_else(|| {
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format!(
|
|
"Expected `UserId` to begin with `id: `, \
|
|
found: {input}",
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)
|
|
})
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})
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.map(|id| Self(id.to_owned()))
|
|
}
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}
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<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
<h3 id="graphqlparse_token_with--fn-or-graphqlparse_tokentypes-attributes"><a class="header" href="#graphqlparse_token_with--fn-or-graphqlparse_tokentypes-attributes"><code>#[graphql(parse_token_with = <fn>]</code> or <code>#[graphql(parse_token(<types>)]</code> attributes</a></h3>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
|
|
</span><span class="boring">use juniper::{
|
|
</span><span class="boring"> GraphQLScalar, InputValue, ParseScalarResult, ParseScalarValue,
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|
</span><span class="boring"> ScalarValue, ScalarToken, Value
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|
</span><span class="boring">};
|
|
</span><span class="boring">
|
|
</span>#[derive(GraphQLScalar)]
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|
#[graphql(
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to_output_with = to_output,
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from_input_with = from_input,
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parse_token_with = parse_token,
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// ^^^^^^^^^^^^^^^^ Can be replaced with `parse_token(String, i32)`
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|
// which tries to parse as `String` and then as `i32`
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// if prior fails.
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)]
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enum StringOrInt {
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|
String(String),
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Int(i32),
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}
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fn to_output<S>(v: &StringOrInt) -> Value<S>
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where
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|
S: ScalarValue
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|
{
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match v {
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|
StringOrInt::String(s) => Value::scalar(s.to_owned()),
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StringOrInt::Int(i) => Value::scalar(*i),
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}
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}
|
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fn from_input<S>(v: &InputValue<S>) -> Result<StringOrInt, String>
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where
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|
S: ScalarValue
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|
{
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v.as_string_value()
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.map(|s| StringOrInt::String(s.into()))
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.or_else(|| v.as_int_value().map(|i| StringOrInt::Int(i)))
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.ok_or_else(|| format!("Expected `String` or `Int`, found: {v}"))
|
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}
|
|
|
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fn parse_token<S: ScalarValue>(value: ScalarToken<'_>) -> ParseScalarResult<S> {
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<String as ParseScalarValue<S>>::from_str(value)
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.or_else(|_| <i32 as ParseScalarValue<S>>::from_str(value))
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}
|
|
<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
<blockquote>
|
|
<p><strong>NOTE:</strong> As you can see, once you provide all 3 custom resolvers, there
|
|
is no need to follow <code>newtype</code> pattern.</p>
|
|
</blockquote>
|
|
<h3 id="graphqlwith--path-attribute"><a class="header" href="#graphqlwith--path-attribute"><code>#[graphql(with = <path>)]</code> attribute</a></h3>
|
|
<p>Instead of providing all custom resolvers, you can provide path to the <code>to_output</code>,
|
|
<code>from_input</code>, <code>parse_token</code> functions.</p>
|
|
<p>Path can be simply <code>with = Self</code> (default path where macro expects resolvers to be),
|
|
in case there is an impl block with custom resolvers:</p>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
|
|
</span><span class="boring">use juniper::{
|
|
</span><span class="boring"> GraphQLScalar, InputValue, ParseScalarResult, ParseScalarValue,
|
|
</span><span class="boring"> ScalarValue, ScalarToken, Value
|
|
</span><span class="boring">};
|
|
</span><span class="boring">
|
|
</span>#[derive(GraphQLScalar)]
|
|
// #[graphql(with = Self)] <- default behaviour
|
|
enum StringOrInt {
|
|
String(String),
|
|
Int(i32),
|
|
}
|
|
|
|
impl StringOrInt {
|
|
fn to_output<S: ScalarValue>(&self) -> Value<S> {
|
|
match self {
|
|
Self::String(s) => Value::scalar(s.to_owned()),
|
|
Self::Int(i) => Value::scalar(*i),
|
|
}
|
|
}
|
|
|
|
fn from_input<S>(v: &InputValue<S>) -> Result<Self, String>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
v.as_string_value()
|
|
.map(|s| Self::String(s.into()))
|
|
.or_else(|| v.as_int_value().map(Self::Int))
|
|
.ok_or_else(|| format!("Expected `String` or `Int`, found: {v}"))
|
|
}
|
|
|
|
fn parse_token<S>(value: ScalarToken<'_>) -> ParseScalarResult<S>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
<String as ParseScalarValue<S>>::from_str(value)
|
|
.or_else(|_| <i32 as ParseScalarValue<S>>::from_str(value))
|
|
}
|
|
}
|
|
<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
<p>Or it can be path to a module, where custom resolvers are located.</p>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
|
|
</span><span class="boring">use juniper::{
|
|
</span><span class="boring"> GraphQLScalar, InputValue, ParseScalarResult, ParseScalarValue,
|
|
</span><span class="boring"> ScalarValue, ScalarToken, Value
|
|
</span><span class="boring">};
|
|
</span><span class="boring">
|
|
</span>#[derive(GraphQLScalar)]
|
|
#[graphql(with = string_or_int)]
|
|
enum StringOrInt {
|
|
String(String),
|
|
Int(i32),
|
|
}
|
|
|
|
mod string_or_int {
|
|
use super::*;
|
|
|
|
pub(super) fn to_output<S>(v: &StringOrInt) -> Value<S>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
match v {
|
|
StringOrInt::String(s) => Value::scalar(s.to_owned()),
|
|
StringOrInt::Int(i) => Value::scalar(*i),
|
|
}
|
|
}
|
|
|
|
pub(super) fn from_input<S>(v: &InputValue<S>) -> Result<StringOrInt, String>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
v.as_string_value()
|
|
.map(|s| StringOrInt::String(s.into()))
|
|
.or_else(|| v.as_int_value().map(StringOrInt::Int))
|
|
.ok_or_else(|| format!("Expected `String` or `Int`, found: {v}"))
|
|
}
|
|
|
|
pub(super) fn parse_token<S>(value: ScalarToken<'_>) -> ParseScalarResult<S>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
<String as ParseScalarValue<S>>::from_str(value)
|
|
.or_else(|_| <i32 as ParseScalarValue<S>>::from_str(value))
|
|
}
|
|
}
|
|
<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
<p>Also, you can partially override <code>#[graphql(with)]</code> attribute with other custom scalars.</p>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
|
|
</span><span class="boring">use juniper::{GraphQLScalar, InputValue, ParseScalarResult, ScalarValue, ScalarToken, Value};
|
|
</span><span class="boring">
|
|
</span>#[derive(GraphQLScalar)]
|
|
#[graphql(parse_token(String, i32))]
|
|
enum StringOrInt {
|
|
String(String),
|
|
Int(i32),
|
|
}
|
|
|
|
impl StringOrInt {
|
|
fn to_output<S>(&self) -> Value<S>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
match self {
|
|
Self::String(s) => Value::scalar(s.to_owned()),
|
|
Self::Int(i) => Value::scalar(*i),
|
|
}
|
|
}
|
|
|
|
fn from_input<S>(v: &InputValue<S>) -> Result<Self, String>
|
|
where
|
|
S: ScalarValue,
|
|
{
|
|
v.as_string_value()
|
|
.map(|s| Self::String(s.into()))
|
|
.or_else(|| v.as_int_value().map(Self::Int))
|
|
.ok_or_else(|| format!("Expected `String` or `Int`, found: {v}"))
|
|
}
|
|
}
|
|
<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
<h3 id="using-foreign-types-as-scalars"><a class="header" href="#using-foreign-types-as-scalars">Using foreign types as scalars</a></h3>
|
|
<p>For implementing custom scalars on foreign types there is <code>#[graphql_scalar]</code> attribute macro.</p>
|
|
<blockquote>
|
|
<p><strong>NOTE:</strong> To satisfy <a href="https://doc.rust-lang.org/reference/items/implementations.html#orphan-rules">orphan rules</a> you should provide local <a href="https://docs.rs/juniper/latest/juniper/trait.ScalarValue.html"><code>ScalarValue</code></a> implementation.</p>
|
|
</blockquote>
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
|
|
</span><span class="boring">mod date {
|
|
</span><span class="boring"> pub struct Date;
|
|
</span><span class="boring"> impl std::str::FromStr for Date {
|
|
</span><span class="boring"> type Err = String;
|
|
</span><span class="boring">
|
|
</span><span class="boring"> fn from_str(_value: &str) -> Result<Self, Self::Err> {
|
|
</span><span class="boring"> unimplemented!()
|
|
</span><span class="boring"> }
|
|
</span><span class="boring"> }
|
|
</span><span class="boring">
|
|
</span><span class="boring"> impl std::fmt::Display for Date {
|
|
</span><span class="boring"> fn fmt(&self, _f: &mut std::fmt::Formatter) -> std::fmt::Result {
|
|
</span><span class="boring"> unimplemented!()
|
|
</span><span class="boring"> }
|
|
</span><span class="boring"> }
|
|
</span><span class="boring">}
|
|
</span><span class="boring">
|
|
</span><span class="boring">use juniper::DefaultScalarValue as CustomScalarValue;
|
|
</span>use juniper::{graphql_scalar, InputValue, ScalarValue, Value};
|
|
|
|
#[graphql_scalar(
|
|
with = date_scalar,
|
|
parse_token(String),
|
|
scalar = CustomScalarValue,
|
|
// ^^^^^^^^^^^^^^^^^ Local `ScalarValue` implementation.
|
|
)]
|
|
type Date = date::Date;
|
|
// ^^^^^^^^^^ Type from another crate.
|
|
|
|
mod date_scalar {
|
|
use super::*;
|
|
|
|
pub(super) fn to_output(v: &Date) -> Value<CustomScalarValue> {
|
|
Value::scalar(v.to_string())
|
|
}
|
|
|
|
pub(super) fn from_input(v: &InputValue<CustomScalarValue>) -> Result<Date, String> {
|
|
v.as_string_value()
|
|
.ok_or_else(|| format!("Expected `String`, found: {v}"))
|
|
.and_then(|s| s.parse().map_err(|e| format!("Failed to parse `Date`: {e}")))
|
|
}
|
|
}
|
|
<span class="boring">
|
|
</span><span class="boring">fn main() {}</span></code></pre></pre>
|
|
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