2019-03-23 08:08:09 -05:00
<!DOCTYPE HTML>
2023-10-06 14:41:48 -05:00
< html lang = "en" class = "light" dir = "ltr" >
2019-03-23 08:08:09 -05:00
< head >
<!-- Book generated using mdBook -->
< meta charset = "UTF-8" >
2024-03-20 11:02:18 -05:00
< title > Unions - Juniper Book< / title >
2023-02-27 13:27:31 -06:00
2022-04-12 11:26:39 -05:00
<!-- Custom HTML head -->
2023-02-27 13:27:31 -06:00
2022-04-12 11:26:39 -05:00
< meta name = "description" content = "User guide for Juniper (GraphQL server library for Rust)." >
2019-03-23 08:08:09 -05:00
< meta name = "viewport" content = "width=device-width, initial-scale=1" >
2023-10-06 14:41:48 -05:00
< meta name = "theme-color" content = "#ffffff" >
2019-03-23 08:08:09 -05:00
2022-04-12 11:26:39 -05:00
< link rel = "icon" href = "../favicon.svg" >
2021-09-25 23:31:16 -05:00
< link rel = "shortcut icon" href = "../favicon.png" >
< link rel = "stylesheet" href = "../css/variables.css" >
2019-03-23 08:08:09 -05:00
< link rel = "stylesheet" href = "../css/general.css" >
< link rel = "stylesheet" href = "../css/chrome.css" >
2021-09-25 23:31:16 -05:00
< link rel = "stylesheet" href = "../css/print.css" media = "print" >
2023-02-27 13:27:31 -06:00
2019-03-23 08:08:09 -05:00
<!-- Fonts -->
< link rel = "stylesheet" href = "../FontAwesome/css/font-awesome.css" >
2022-04-12 11:26:39 -05:00
< link rel = "stylesheet" href = "../fonts/fonts.css" >
2023-02-27 13:27:31 -06:00
2019-03-23 08:08:09 -05:00
<!-- Highlight.js Stylesheets -->
< link rel = "stylesheet" href = "../highlight.css" >
< link rel = "stylesheet" href = "../tomorrow-night.css" >
< link rel = "stylesheet" href = "../ayu-highlight.css" >
<!-- Custom theme stylesheets -->
2023-02-27 13:27:31 -06:00
2021-09-25 23:31:16 -05:00
< / head >
2023-10-06 14:41:48 -05:00
< body class = "sidebar-visible no-js" >
2023-02-27 13:27:31 -06:00
< div id = "body-container" >
2019-03-23 08:08:09 -05:00
<!-- Provide site root to javascript -->
2023-02-27 13:27:31 -06:00
< script >
2022-04-12 11:26:39 -05:00
var path_to_root = "../";
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
< / script >
2019-03-23 08:08:09 -05:00
<!-- Work around some values being stored in localStorage wrapped in quotes -->
2023-02-27 13:27:31 -06:00
< script >
2019-03-23 08:08:09 -05:00
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') & & theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') & & sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
< / script >
<!-- Set the theme before any content is loaded, prevents flash -->
2023-02-27 13:27:31 -06:00
< script >
2019-03-23 08:08:09 -05:00
var theme;
2022-04-12 11:26:39 -05:00
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('light')
html.classList.add(theme);
2023-10-06 14:41:48 -05:00
var body = document.querySelector('body');
body.classList.remove('no-js')
body.classList.add('js');
2019-03-23 08:08:09 -05:00
< / script >
2023-10-06 14:41:48 -05:00
< input type = "checkbox" id = "sidebar-toggle-anchor" class = "hidden" >
2019-03-23 08:08:09 -05:00
<!-- Hide / unhide sidebar before it is displayed -->
2023-02-27 13:27:31 -06:00
< script >
2023-10-06 14:41:48 -05:00
var body = document.querySelector('body');
2023-04-04 07:07:31 -05:00
var sidebar = null;
2023-10-06 14:41:48 -05:00
var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
2019-03-23 08:08:09 -05:00
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
2023-04-04 07:07:31 -05:00
} else {
sidebar = 'hidden';
2019-03-23 08:08:09 -05:00
}
2023-10-06 14:41:48 -05:00
sidebar_toggle.checked = sidebar === 'visible';
body.classList.remove('sidebar-visible');
body.classList.add("sidebar-" + sidebar);
2019-03-23 08:08:09 -05:00
< / script >
< nav id = "sidebar" class = "sidebar" aria-label = "Table of contents" >
2022-04-12 11:26:39 -05:00
< div class = "sidebar-scrollbox" >
2024-03-20 11:02:18 -05:00
< ol class = "chapter" > < li class = "chapter-item expanded " > < a href = "../introduction.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/index.html" > < strong aria-hidden = "true" > 3.1.< / strong > 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/context.html" > < strong aria-hidden = "true" > 3.1.2.< / strong > Context< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/error/index.html" > < strong aria-hidden = "true" > 3.1.3.< / strong > Error handling< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../types/objects/error/field.html" > < strong aria-hidden = "true" > 3.1.3.1.< / strong > Field errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/error/schema.html" > < strong aria-hidden = "true" > 3.1.3.2.< / strong > Schema errors< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/generics.html" > < strong aria-hidden = "true" > 3.1.4.< / strong > Generics< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../types/interfaces.html" > < strong aria-hidden = "true" > 3.2.< / strong > Interfaces< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/unions.html" class = "active" > < strong aria-hidden = "true" > 3.3.< / strong > Unions< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/enums.html" > < strong aria-hidden = "true" > 3.4.< / strong > Enums< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/input_objects.html" > < strong aria-hidden = "true" > 3.5.< / strong > Input objects< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/scalars.html" > < strong aria-hidden = "true" > 3.6.< / strong > Scalars< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../schema/index.html" > < strong aria-hidden = "true" > 4.< / strong > Schema< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../schema/subscriptions.html" > < strong aria-hidden = "true" > 4.1.< / strong > Subscriptions< / a > < / li > < li class = "chapter-item expanded " > < a href = "../schema/introspection.html" > < strong aria-hidden = "true" > 4.2.< / strong > Introspection< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../serve/index.html" > < strong aria-hidden = "true" > 5.< / strong > Serving< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../serve/batching.html" > < strong aria-hidden = "true" > 5.1.< / strong > Batching< / 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/implicit_and_explicit_null.html" > < strong aria-hidden = "true" > 6.1.< / strong > Implicit and explicit null< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/n_plus_1.html" > < strong aria-hidden = "true" > 6.2.< / strong > N+1 problem< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../advanced/dataloader.html" > < strong aria-hidden = "true" > 6.2.1.< / strong > DataLoader< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/lookahead.html" > < strong aria-hidden = "true" > 6.2.2.< / strong > Look-ahead< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../advanced/eager_loading.html" > < strong aria-hidden = "true" > 6.2.2.1.< / strong > Eager loading< / a > < / li > < / ol > < / li > < / ol > < / li > < / ol > < / li > < / ol >
2022-04-12 11:26:39 -05:00
< / div >
2023-11-30 15:24:02 -06:00
< div id = "sidebar-resize-handle" class = "sidebar-resize-handle" >
< div class = "sidebar-resize-indicator" > < / div >
< / div >
2019-03-23 08:08:09 -05:00
< / nav >
2023-07-07 07:41:41 -05:00
<!-- Track and set sidebar scroll position -->
< script >
var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
sidebarScrollbox.addEventListener('click', function(e) {
if (e.target.tagName === 'A') {
sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
}
}, { passive: true });
var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
sessionStorage.removeItem('sidebar-scroll');
if (sidebarScrollTop) {
// preserve sidebar scroll position when navigating via links within sidebar
sidebarScrollbox.scrollTop = sidebarScrollTop;
} else {
// scroll sidebar to current active section when navigating via "next/previous chapter" buttons
var activeSection = document.querySelector('#sidebar .active');
if (activeSection) {
activeSection.scrollIntoView({ block: 'center' });
}
}
< / script >
2019-03-23 08:08:09 -05:00
< div id = "page-wrapper" class = "page-wrapper" >
< div class = "page" >
2023-02-27 13:27:31 -06:00
< div id = "menu-bar-hover-placeholder" > < / div >
2023-07-07 07:41:41 -05:00
< div id = "menu-bar" class = "menu-bar sticky" >
2022-04-12 11:26:39 -05:00
< div class = "left-buttons" >
2023-10-06 14:41:48 -05:00
< label id = "sidebar-toggle" class = "icon-button" for = "sidebar-toggle-anchor" title = "Toggle Table of Contents" aria-label = "Toggle Table of Contents" aria-controls = "sidebar" >
2022-04-12 11:26:39 -05:00
< i class = "fa fa-bars" > < / i >
2023-10-06 14:41:48 -05:00
< / label >
2022-04-12 11:26:39 -05:00
< button id = "theme-toggle" class = "icon-button" type = "button" title = "Change theme" aria-label = "Change theme" aria-haspopup = "true" aria-expanded = "false" aria-controls = "theme-list" >
< i class = "fa fa-paint-brush" > < / i >
< / button >
< ul id = "theme-list" class = "theme-popup" aria-label = "Themes" role = "menu" >
2023-02-27 13:27:31 -06:00
< li role = "none" > < button role = "menuitem" class = "theme" id = "light" > Light< / button > < / li >
2022-04-12 11:26:39 -05:00
< li role = "none" > < button role = "menuitem" class = "theme" id = "rust" > Rust< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "coal" > Coal< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "navy" > Navy< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "ayu" > Ayu< / button > < / li >
< / ul >
< button id = "search-toggle" class = "icon-button" type = "button" title = "Search. (Shortkey: s)" aria-label = "Toggle Searchbar" aria-expanded = "false" aria-keyshortcuts = "S" aria-controls = "searchbar" >
< i class = "fa fa-search" > < / i >
< / button >
< / div >
2024-03-20 11:02:18 -05:00
< h1 class = "menu-title" > Juniper Book< / h1 >
2022-04-12 11:26:39 -05:00
< div class = "right-buttons" >
< a href = "../print.html" title = "Print this book" aria-label = "Print this book" >
< i id = "print-button" class = "fa fa-print" > < / i >
< / a >
2023-02-27 13:27:31 -06:00
2019-03-23 08:08:09 -05:00
< / div >
< / div >
2021-09-25 23:31:16 -05:00
< div id = "search-wrapper" class = "hidden" >
2019-03-23 08:08:09 -05:00
< form id = "searchbar-outer" class = "searchbar-outer" >
2022-04-12 11:26:39 -05:00
< input type = "search" id = "searchbar" name = "searchbar" placeholder = "Search this book ..." aria-controls = "searchresults-outer" aria-describedby = "searchresults-header" >
2019-03-23 08:08:09 -05:00
< / form >
< div id = "searchresults-outer" class = "searchresults-outer hidden" >
< div id = "searchresults-header" class = "searchresults-header" > < / div >
< ul id = "searchresults" >
< / ul >
< / div >
< / div >
2023-02-27 13:27:31 -06:00
2019-03-23 08:08:09 -05:00
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
2023-02-27 13:27:31 -06:00
< script >
2019-03-23 08:08:09 -05:00
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
< / script >
< div id = "content" class = "content" >
< main >
2022-04-12 11:26:39 -05:00
< h1 id = "unions" > < a class = "header" href = "#unions" > Unions< / a > < / h1 >
2024-03-20 11:02:18 -05:00
< blockquote >
< p > < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL unions< / a > represent an object that could be one of a list of < a href = "https://spec.graphql.org/October2021#sec-Objects" > GraphQL object< / a > types, but provides for no guaranteed fields between those types. They also differ from < a href = "https://spec.graphql.org/October2021#sec-Interfaces" > interfaces< / a > in that < a href = "https://spec.graphql.org/October2021#sec-Objects" > object< / a > types declare what < a href = "https://spec.graphql.org/October2021#sec-Interfaces" > interfaces< / a > they implement, but are not aware of what < a href = "https://spec.graphql.org/October2021#sec-Unions" > unions< / a > contain them.< / p >
< / blockquote >
< p > From the server's point of view, < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL unions< / a > are somewhat similar to < a href = "https://spec.graphql.org/October2021#sec-Interfaces" > interfaces< / a > : the main difference is that they don't contain fields on their own, and so, we only need to represent a value, < em > dispatchable< / em > into concrete < a href = "https://spec.graphql.org/October2021#sec-Objects" > objects< / a > .< / p >
2024-04-04 08:25:34 -05:00
< p > Obviously, the most straightforward approach to express < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL unions< / a > in < a href = "https://www.rust-lang.org" > Rust< / a > is to use < a href = "https://doc.rust-lang.org/reference/items/enumerations.html#enumerations" > enums< / a > . In < a href = "https://docs.rs/juniper" > Juniper< / a > this may be done by using < a href = "https://docs.rs/juniper/0.16.1/juniper/derive.GraphQLUnion.html" > < code > #[derive(GraphQLInterface)]< / code > < / a > attribute on them:< / p >
2024-03-20 11:02:18 -05:00
< pre > < pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > extern crate derive_more;
< / span > < span class = "boring" > extern crate juniper;
< / span > < span class = "boring" > use derive_more::From;
< / span > < span class = "boring" > use juniper::{GraphQLObject, GraphQLUnion};
< / span > < span class = "boring" >
< / span > #[derive(GraphQLObject)]
2019-03-23 08:08:09 -05:00
struct Human {
id: String,
home_planet: String,
}
2020-06-04 03:28:07 -05:00
#[derive(GraphQLObject)]
2019-03-23 08:08:09 -05:00
struct Droid {
id: String,
primary_function: String,
}
2020-06-04 03:28:07 -05:00
#[derive(From, GraphQLUnion)]
2024-03-20 11:02:18 -05:00
// ^^^^ only for convenience, and may be omitted
2020-06-04 03:28:07 -05:00
enum Character {
Human(Human),
Droid(Droid),
}
2022-04-12 11:26:39 -05:00
< span class = "boring" >
2023-02-27 13:27:31 -06:00
< / span > < span class = "boring" > fn main() {}< / span > < / code > < / pre > < / pre >
2024-03-20 11:02:18 -05:00
< h3 id = "renaming" > < a class = "header" href = "#renaming" > Renaming< / a > < / h3 >
< p > Just as with < a href = "objects/index.html#renaming" > renaming GraphQL objects< / a > , we can override the default < a href = "https://spec.graphql.org/October2021#sec-Unions" > union< / a > name by using the < code > #[graphql(name = "...")]< / code > attribute:< / p >
2022-07-13 09:04:13 -05:00
< pre > < pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > extern crate juniper;
2024-03-20 11:02:18 -05:00
< / span > < span class = "boring" > use juniper::{GraphQLObject, GraphQLUnion};
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(GraphQLObject)]
< / span > < span class = "boring" > struct Human {
< / span > < span class = "boring" > id: String,
< / span > < span class = "boring" > home_planet: String,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(GraphQLObject)]
< / span > < span class = "boring" > struct Droid {
< / span > < span class = "boring" > id: String,
< / span > < span class = "boring" > primary_function: String,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > #[derive(GraphQLUnion)]
#[graphql(name = "CharacterUnion")]
enum Character { // exposed as `CharacterUnion` in GraphQL schema
2020-06-04 03:28:07 -05:00
Human(Human),
Droid(Droid),
2019-03-23 08:08:09 -05:00
}
2022-04-12 11:26:39 -05:00
< span class = "boring" >
2023-02-27 13:27:31 -06:00
< / span > < span class = "boring" > fn main() {}< / span > < / code > < / pre > < / pre >
2024-03-20 11:02:18 -05:00
< blockquote >
< p > < strong > NOTE< / strong > : Unlike < a href = "https://doc.rust-lang.org/reference/items/enumerations.html#enumerations" > Rust enum variants< / a > , < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL union members< / a > don't have any special names aside from the ones provided by < a href = "https://spec.graphql.org/October2021#sec-Objects" > objects< / a > themselves, and so, obviously, < strong > cannot be renamed< / strong > .< / p >
< / blockquote >
< h3 id = "documentation" > < a class = "header" href = "#documentation" > Documentation< / a > < / h3 >
< p > Similarly to < a href = "objects/index.html#documentation" > documenting GraphQL objects< / a > , we can < a href = "https://spec.graphql.org/October2021#sec-Descriptions" > document< / a > a < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL union< / a > via < code > #[graphql(description = "...")]< / code > attribute or < 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, GraphQLUnion};
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(GraphQLObject)]
< / span > < span class = "boring" > struct Human {
< / span > < span class = "boring" > id: String,
< / span > < span class = "boring" > home_planet: String,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(GraphQLObject)]
< / span > < span class = "boring" > struct Droid {
< / span > < span class = "boring" > id: String,
< / span > < span class = "boring" > primary_function: String,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > /// This doc comment is visible in both Rust API docs and GraphQL schema
/// descriptions.
2020-06-04 03:28:07 -05:00
#[derive(GraphQLUnion)]
enum Character {
2024-03-20 11:02:18 -05:00
/// This doc comment is visible only in Rust API docs.
2020-06-04 03:28:07 -05:00
Human(Human),
2024-03-20 11:02:18 -05:00
/// This doc comment is visible only in Rust API docs.
2020-06-04 03:28:07 -05:00
Droid(Droid),
}
2024-03-20 11:02:18 -05:00
/// This doc comment is visible only in Rust API docs.
2020-06-04 03:28:07 -05:00
#[derive(GraphQLUnion)]
2024-03-20 11:02:18 -05:00
#[graphql(description = "This description overwrites the one from doc comment.")]
// ^^^^^^^^^^^ or `desc` shortcut, up to your preference
enum Person {
/// This doc comment is visible only in Rust API docs.
2020-06-04 03:28:07 -05:00
Human(Human),
}
2022-04-12 11:26:39 -05:00
< span class = "boring" >
2023-02-27 13:27:31 -06:00
< / span > < span class = "boring" > fn main() {}< / span > < / code > < / pre > < / pre >
2020-06-04 03:28:07 -05:00
< blockquote >
2024-03-20 11:02:18 -05:00
< p > < strong > NOTE< / strong > : Unlike < a href = "https://doc.rust-lang.org/reference/items/enumerations.html#enumerations" > Rust enum variants< / a > , < a href = "https://spec.graphql.org/October2021#sec-Unions" > GraphQL union members< / a > don't have any special constructors aside from the provided < a href = "https://spec.graphql.org/October2021#sec-Objects" > objects< / a > directly, and so, < strong > cannot be < a href = "https://spec.graphql.org/October2021#sec-Descriptions" > documented< / a > < / strong > , but rather reuse < a href = "https://spec.graphql.org/October2021#sec-Descriptions" > object descriptions< / a > "as is".< / p >
2020-06-04 03:28:07 -05:00
< / blockquote >
2024-03-20 11:02:18 -05:00
< h3 id = "ignoring" > < a class = "header" href = "#ignoring" > Ignoring< / a > < / h3 >
< p > In some rare situations we may want to omit exposing an < a href = "https://doc.rust-lang.org/reference/items/enumerations.html#enumerations" > enum< / a > variant in a < a href = "https://graphql.org/learn/schema" > GraphQL schema< / a > . < a href = "enums.html#ignoring" > Similarly to GraphQL enums< / a > , we can just annotate the variant with the < code > #[graphql(ignore)]< / code > attribute.< / p >
< p > As an example, let's consider the situation where we need to bind some type parameter < code > T< / code > for doing interesting type-level stuff in our resolvers. To achieve this we need to have < code > PhantomData< T> < / code > , but we don't want it exposed in the GraphQL schema.< / p >
< pre > < pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > extern crate derive_more;
2022-04-12 11:26:39 -05:00
< / span > < span class = "boring" > extern crate juniper;
2024-03-20 11:02:18 -05:00
< / span > < span class = "boring" > use std::marker::PhantomData;
< / span > < span class = "boring" > use derive_more::From;
< / span > < span class = "boring" > use juniper::{GraphQLObject, GraphQLUnion};
< / span > < span class = "boring" >
< / span > #[derive(GraphQLObject)]
2020-04-15 03:07:36 -05:00
struct Human {
id: String,
home_planet: String,
}
2020-06-04 03:28:07 -05:00
#[derive(GraphQLObject)]
2020-04-15 03:07:36 -05:00
struct Droid {
id: String,
primary_function: String,
}
2024-03-20 11:02:18 -05:00
#[derive(From, GraphQLUnion)]
enum Character< S> {
2020-04-15 03:07:36 -05:00
Human(Human),
Droid(Droid),
2024-03-20 11:02:18 -05:00
#[from(ignore)]
#[graphql(ignore)]
// ^^^^^^ or `skip`, up to your preference
_State(PhantomData< S> ),
2020-04-15 03:07:36 -05:00
}
2022-04-12 11:26:39 -05:00
< span class = "boring" >
2023-02-27 13:27:31 -06:00
< / span > < span class = "boring" > fn main() {}< / span > < / code > < / pre > < / pre >
2024-03-20 11:02:18 -05:00
< blockquote >
< p > < strong > WARNING< / strong > : It's the < em > library user's responsibility< / em > to ensure that ignored < a href = "https://doc.rust-lang.org/reference/items/enumerations.html#enumerations" > enum< / a > variant is < strong > never< / strong > returned from resolvers, otherwise resolving the < a href = "https://graphql.org" > GraphQL< / a > query will < strong > panic in runtime< / strong > .< / p >
< / blockquote >
< blockquote >
2024-04-04 08:25:34 -05:00
< 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.GraphQLUnion.html" > < code > #[derive(GraphQLUnion)]< / code > < / a > attribute.< / p >
2024-03-20 11:02:18 -05:00
< / blockquote >
2019-03-23 08:08:09 -05:00
< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
2024-03-20 11:02:18 -05:00
< a rel = "prev" href = "../types/interfaces.html" class = "mobile-nav-chapters previous" title = "Previous chapter" aria-label = "Previous chapter" aria-keyshortcuts = "Left" >
2019-03-23 08:08:09 -05:00
< i class = "fa fa-angle-left" > < / i >
< / a >
2023-02-27 13:27:31 -06:00
2024-03-20 11:02:18 -05:00
< a rel = "next prefetch" href = "../types/enums.html" class = "mobile-nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
2022-03-04 10:32:21 -06:00
< i class = "fa fa-angle-right" > < / i >
< / a >
2023-02-27 13:27:31 -06:00
2019-03-23 08:08:09 -05:00
< div style = "clear: both" > < / div >
< / nav >
< / div >
< / div >
< nav class = "nav-wide-wrapper" aria-label = "Page navigation" >
2024-03-20 11:02:18 -05:00
< a rel = "prev" href = "../types/interfaces.html" class = "nav-chapters previous" title = "Previous chapter" aria-label = "Previous chapter" aria-keyshortcuts = "Left" >
2019-03-23 08:08:09 -05:00
< i class = "fa fa-angle-left" > < / i >
< / a >
2023-02-27 13:27:31 -06:00
2024-03-20 11:02:18 -05:00
< a rel = "next prefetch" href = "../types/enums.html" class = "nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
2022-03-04 10:32:21 -06:00
< i class = "fa fa-angle-right" > < / i >
< / a >
2021-09-25 23:31:16 -05:00
< / nav >
2019-03-23 08:08:09 -05:00
< / div >
2023-02-27 13:27:31 -06:00
< script >
2022-04-12 11:26:39 -05:00
window.playground_copyable = true;
< / script >
2023-02-27 13:27:31 -06:00
< script src = "../elasticlunr.min.js" > < / script >
< script src = "../mark.min.js" > < / script >
< script src = "../searcher.js" > < / script >
< script src = "../clipboard.min.js" > < / script >
< script src = "../highlight.js" > < / script >
< script src = "../book.js" > < / script >
2019-03-23 08:08:09 -05:00
<!-- Custom JS scripts -->
2023-02-27 13:27:31 -06:00
< / div >
2019-03-23 08:08:09 -05:00
< / body >
< / html >
