<olclass="chapter"><liclass="affix"><ahref="../index.html">Introduction</a></li><liclass="affix"><ahref="../quickstart.html">Quickstart</a></li><liclass="affix"><ahref="../types/index.html">Type System</a></li><li><ahref="../types/objects/defining_objects.html"><strongaria-hidden="true">1.</strong> Defining objects</a></li><li><olclass="section"><li><ahref="../types/objects/complex_fields.html"><strongaria-hidden="true">1.1.</strong> Complex fields</a></li><li><ahref="../types/objects/using_contexts.html"><strongaria-hidden="true">1.2.</strong> Using contexts</a></li><li><ahref="../types/objects/error_handling.html"><strongaria-hidden="true">1.3.</strong> Error handling</a></li></ol></li><li><ahref="../types/other-index.html"><strongaria-hidden="true">2.</strong> Other types</a></li><li><olclass="section"><li><ahref="../types/enums.html"><strongaria-hidden="true">2.1.</strong> Enums</a></li><li><ahref="../types/interfaces.html"><strongaria-hidden="true">2.2.</strong> Interfaces</a></li><li><ahref="../types/input_objects.html"><strongaria-hidden="true">2.3.</strong> Input objects</a></li><li><ahref="../types/scalars.html"><strongaria-hidden="true">2.4.</strong> Scalars</a></li><li><ahref="../types/unions.html"><strongaria-hidden="true">2.5.</strong> Unions</a></li></ol></li><li><ahref="../schema/schemas_and_mutations.html"class="active"><strongaria-hidden="true">3.</strong> Schemas and mutations</a></li><li><ahref="../servers/index.html"><strongaria-hidden="true">4.</strong> Adding A Server</a></li><li><olclass="section"><li><ahref="../servers/official.html"><strongaria-hidden="true">4.1.</strong> Official Server Integrations</a></li><li><olclass="section"><li><ahref="../servers/warp.html"><strongaria-hidden="true">4.1.1.</strong> Warp</a></li><li><ahref="../servers/rocket.html"><strongaria-hidden="true">4.1.2.</strong> Rocket</a></li><li><ahref="../servers/iron.html"><strongaria-hidden="true">4.1.3.</strong> Iron</a></li><li><ahref="../servers/hyper.html"><strongaria-hidden="true">4.1.4.</strong> Hyper</a></li></ol></li><li><ahref="../servers/third-party.html"><strongaria-hidden="true">4.2.</strong> Third Party Integrations</a></li></ol></li><li><ahref="../advanced/index.html"><strongaria-hidden="true">5.</strong> Advanced Topics</a></li><li><olclass="section"><li><ahref="../advanced/introspection.html"><strongaria-hidden="true">5.1.</strong> Introspection</a></li><li><ahref="../advanced/non_struct_objects.html"><strongaria-hidden="true">5.2.</strong> Non-struct objects</a></li><li><ahref="../advanced/objects_and_generics.html"><strongaria-hidden="true">5.3.</strong> Objects and generics</a></li><li><ahref="../advanced/multiple_ops_per_request.html"><strongaria-hidden="true">5.4.</strong> Multiple operations per request</a></li><li><ahref="../advanced/dataloaders.html"><strongaria-hidden="true">5.5.</strong> Dataloaders</a></li><li><ahref="../advanced/subscriptions.html"><strongaria-hidden="true">5.6.</strong> Subscriptions</a></li></ol></li></ol>
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<p>Juniper follows a <ahref="https://blog.logrocket.com/code-first-vs-schema-first-development-graphql/">code-first approach</a> to defining GraphQL schemas. If you would like to use a <ahref="https://blog.logrocket.com/code-first-vs-schema-first-development-graphql/">schema-first approach</a> instead, consider <ahref="https://github.com/davidpdrsn/juniper-from-schema">juniper-from-schema</a> for generating code from a schema file.</p>
<p>A schema consists of three types: a query object, a mutation object, and a subscription object.
These three define the root query fields, mutations and subscriptions of the schema, respectively.</p>
<p>The usage of subscriptions is a little different from the mutation and query objects, so there is a specific <ahref="../advanced/subscriptions.html">section</a> that discusses them.</p>
other object in Juniper. The mutation and subscription object, however, is optional since schemas
can be read-only and without subscriptions as well. If mutations/subscriptions functionality is not needed, consider using <ahref="https://docs.rs/juniper/0.14.2/juniper/struct.EmptyMutation.html">EmptyMutation</a>/[EmptySubscription][EmptySubscription].</p>
<aclass="header"href="#converting-a-rust-schema-to-the-a-hrefhttpsgraphqlorglearnschematype-languagegraphql-schema-languagea"id="converting-a-rust-schema-to-the-a-hrefhttpsgraphqlorglearnschematype-languagegraphql-schema-languagea"><h1>Converting a Rust schema to the <ahref="https://graphql.org/learn/schema/#type-language">GraphQL Schema Language</a></h1></a>
<p>Many tools in the GraphQL ecosystem require the schema to be defined in the <ahref="https://graphql.org/learn/schema/#type-language">GraphQL Schema Language</a>. You can generate a <ahref="https://graphql.org/learn/schema/#type-language">GraphQL Schema Language</a> representation of your schema defined in Rust using the <code>schema-language</code> feature (on by default):</p>
<pre><preclass="playpen"><codeclass="language-rust"># // Only needed due to 2018 edition because the macro is not accessible.
# #[macro_use] extern crate juniper;
use juniper::{FieldResult, EmptyMutation, EmptySubscription, RootNode};
