2019-03-23 08:08:09 -05:00
<!DOCTYPE HTML>
2022-02-24 09:16:21 -06:00
< html lang = "en" class = "sidebar-visible no-js light" >
2019-03-23 08:08:09 -05:00
< head >
<!-- Book generated using mdBook -->
< meta charset = "UTF-8" >
< title > Interfaces - Juniper - GraphQL Server for Rust< / title >
2022-02-24 09:16:21 -06:00
<!-- Custom HTML head -->
2019-03-23 08:08:09 -05:00
< meta content = "text/html; charset=utf-8" http-equiv = "Content-Type" >
< meta name = "description" content = "Documentation for juniper, a GraphQL server library for Rust." >
< meta name = "viewport" content = "width=device-width, initial-scale=1" >
< meta name = "theme-color" content = "#ffffff" / >
2022-02-24 09:16:21 -06:00
< 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" >
2019-03-23 08:08:09 -05:00
<!-- Fonts -->
< link rel = "stylesheet" href = "../FontAwesome/css/font-awesome.css" >
2022-02-24 09:16:21 -06:00
< link rel = "stylesheet" href = "../fonts/fonts.css" >
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 -->
2021-09-25 23:31:16 -05:00
< / head >
2022-02-24 09:16:21 -06:00
< body >
2019-03-23 08:08:09 -05:00
<!-- Provide site root to javascript -->
2022-02-24 09:16:21 -06:00
< script type = "text/javascript" >
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 -->
< script type = "text/javascript" >
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 -->
< script type = "text/javascript" >
var theme;
2022-02-24 09:16:21 -06:00
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('no-js')
html.classList.remove('light')
html.classList.add(theme);
html.classList.add('js');
2019-03-23 08:08:09 -05:00
< / script >
<!-- Hide / unhide sidebar before it is displayed -->
< script type = "text/javascript" >
var html = document.querySelector('html');
var sidebar = 'hidden';
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
}
html.classList.remove('sidebar-visible');
html.classList.add("sidebar-" + sidebar);
< / script >
< nav id = "sidebar" class = "sidebar" aria-label = "Table of contents" >
2022-02-24 09:16:21 -06:00
< div class = "sidebar-scrollbox" >
< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Introduction< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../quickstart.html" > Quickstart< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../types/index.html" > Type System< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/defining_objects.html" > < strong aria-hidden = "true" > 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" > 1.1.< / strong > Complex fields< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/using_contexts.html" > < strong aria-hidden = "true" > 1.2.< / strong > Using contexts< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/error_handling.html" > < strong aria-hidden = "true" > 1.3.< / strong > Error handling< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../types/other-index.html" > < strong aria-hidden = "true" > 2.< / strong > Other types< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../types/enums.html" > < strong aria-hidden = "true" > 2.1.< / strong > Enums< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/interfaces.html" class = "active" > < strong aria-hidden = "true" > 2.2.< / strong > Interfaces< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/input_objects.html" > < strong aria-hidden = "true" > 2.3.< / strong > Input objects< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/scalars.html" > < strong aria-hidden = "true" > 2.4.< / strong > Scalars< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/unions.html" > < strong aria-hidden = "true" > 2.5.< / strong > Unions< / a > < / li > < / ol > < / li > < / ol >
< / div >
< div id = "sidebar-resize-handle" class = "sidebar-resize-handle" > < / div >
2019-03-23 08:08:09 -05:00
< / nav >
< div id = "page-wrapper" class = "page-wrapper" >
< div class = "page" >
2022-02-24 09:16:21 -06:00
< div id = "menu-bar-hover-placeholder" > < / div >
< div id = "menu-bar" class = "menu-bar sticky bordered" >
< div class = "left-buttons" >
< button id = "sidebar-toggle" class = "icon-button" type = "button" title = "Toggle Table of Contents" aria-label = "Toggle Table of Contents" aria-controls = "sidebar" >
< i class = "fa fa-bars" > < / i >
< / button >
< 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" >
< li role = "none" > < button role = "menuitem" class = "theme" id = "light" > Light (default)< / button > < / li >
< 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 >
< h1 class = "menu-title" > Juniper - GraphQL Server for Rust< / h1 >
< 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 >
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" >
2022-02-24 09:16:21 -06:00
< 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 >
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
< script type = "text/javascript" >
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 >
2022-02-24 09:16:21 -06:00
< h1 id = "interfaces" > < a class = "header" href = "#interfaces" > Interfaces< / a > < / h1 >
2020-10-06 05:18:31 -05:00
< p > < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interfaces< / a > map well to interfaces known from common object-oriented languages such as Java or C#, but Rust, unfortunately, has no concept that maps perfectly to them. The nearest analogue of < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interfaces< / a > are Rust traits, and the main difference is that in GraphQL an < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > interface type< / a > serves both as an < em > abstraction< / em > and a < em > boxed value (downcastable to concrete implementers)< / em > , while in Rust, a trait is an < em > abstraction only< / em > and < em > to represent such a boxed value a separate type is required< / em > , like enum or trait object, because Rust trait doesn't represent a type itself, and so can have no values. This difference imposes some unintuitive and non-obvious corner cases when we try to express < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interfaces< / a > in Rust, but on the other hand gives you full control over which type is backing your interface, and how it's resolved.< / p >
< p > For implementing < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interfaces< / a > Juniper provides the < code > #[graphql_interface]< / code > macro.< / p >
2022-02-24 09:16:21 -06:00
< h2 id = "traits" > < a class = "header" href = "#traits" > Traits< / a > < / h2 >
2020-10-06 05:18:31 -05:00
< p > Defining a trait is mandatory for defining a < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > , because this is the < em > obvious< / em > way we describe an < em > abstraction< / em > in Rust. All < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > interface< / a > fields are defined as computed ones via trait methods.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::graphql_interface;
2020-10-06 05:18:31 -05:00
#[graphql_interface]
trait Character {
fn id(& self) -> & str;
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
2020-10-06 05:18:31 -05:00
< p > However, to return values of such < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > interface< / a > , we should provide its implementers and the Rust type representing a < em > boxed value of this trait< / em > . The last one can be represented in two flavors: enum and < a href = "https://doc.rust-lang.org/reference/types/trait-object.html" > trait object< / a > .< / p >
2022-02-24 09:16:21 -06:00
< h3 id = "enum-values-default" > < a class = "header" href = "#enum-values-default" > Enum values (default)< / a > < / h3 >
2020-10-06 05:18:31 -05:00
< p > By default, Juniper generates an enum representing the values of the defined < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > , and names it straightforwardly, < code > {Interface}Value< / code > .< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::{graphql_interface, GraphQLObject};
2020-10-06 05:18:31 -05:00
#[graphql_interface(for = [Human, Droid])] // enumerating all implementers is mandatory
trait Character {
fn id(& self) -> & str;
}
#[derive(GraphQLObject)]
#[graphql(impl = CharacterValue)] // notice enum name, NOT trait name
2019-03-23 08:08:09 -05:00
struct Human {
id: String,
2020-10-06 05:18:31 -05:00
}
2019-03-23 08:08:09 -05:00
2020-10-06 05:18:31 -05:00
#[derive(GraphQLObject)]
#[graphql(impl = CharacterValue)]
2019-03-23 08:08:09 -05:00
struct Droid {
id: String,
2020-10-06 05:18:31 -05:00
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
2020-10-06 05:18:31 -05:00
< p > Also, enum name can be specified explicitly, if desired.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::{graphql_interface, GraphQLObject};
2020-10-06 05:18:31 -05:00
#[graphql_interface(enum = CharaterInterface, for = Human)]
2019-03-23 08:08:09 -05:00
trait Character {
fn id(& self) -> & str;
2020-10-06 05:18:31 -05:00
}
2019-03-23 08:08:09 -05:00
2020-10-06 05:18:31 -05:00
#[derive(GraphQLObject)]
#[graphql(impl = CharaterInterface)]
struct Human {
id: String,
home_planet: String,
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
< h3 id = "ignoring-trait-methods" > < a class = "header" href = "#ignoring-trait-methods" > Ignoring trait methods< / a > < / h3 >
2020-10-06 05:18:31 -05:00
< p > We may want to omit some trait methods to be assumed as < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > fields and ignore them.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::{graphql_interface, GraphQLObject};
2020-10-06 05:18:31 -05:00
#[graphql_interface(for = Human)]
trait Character {
fn id(& self) -> & str;
2019-03-23 08:08:09 -05:00
2020-11-14 07:58:04 -06:00
#[graphql(ignore)] // or `#[graphql(skip)]`, your choice
2020-10-06 05:18:31 -05:00
fn ignored(& self) -> u32 { 0 }
}
2019-03-23 08:08:09 -05:00
2020-10-06 05:18:31 -05:00
#[derive(GraphQLObject)]
#[graphql(impl = CharacterValue)]
2019-03-23 08:08:09 -05:00
struct Human {
id: String,
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
< h3 id = "fields-arguments-and-interface-customization" > < a class = "header" href = "#fields-arguments-and-interface-customization" > Fields, arguments and interface customization< / a > < / h3 >
2020-10-06 05:18:31 -05:00
< p > Similarly to < a href = "https://spec.graphql.org/June2018/#sec-Objects" > GraphQL objects< / a > Juniper allows to fully customize < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > interface< / a > fields and their arguments.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > #![allow(deprecated)]
< / span > < span class = "boring" > extern crate juniper;
< / span > use juniper::graphql_interface;
2020-10-06 05:18:31 -05:00
// Renames the interface in GraphQL schema.
#[graphql_interface(name = " MyCharacter" )]
// Describes the interface in GraphQL schema.
#[graphql_interface(description = " My own character." )]
// Usual Rust docs are supported too as GraphQL interface description,
// but `description` attribute argument takes precedence over them, if specified.
/// This doc is absent in GraphQL schema.
trait Character {
// Renames the field in GraphQL schema.
2020-11-14 07:58:04 -06:00
#[graphql(name = " myId" )]
2020-10-06 05:18:31 -05:00
// Deprecates the field in GraphQL schema.
// Usual Rust `#[deprecated]` attribute is supported too as field deprecation,
// but `deprecated` attribute argument takes precedence over it, if specified.
2020-11-14 07:58:04 -06:00
#[graphql(deprecated = " Do not use it." )]
2020-10-06 05:18:31 -05:00
// Describes the field in GraphQL schema.
2020-11-14 07:58:04 -06:00
#[graphql(description = " ID of my own character." )]
2020-10-06 05:18:31 -05:00
// Usual Rust docs are supported too as field description,
// but `description` attribute argument takes precedence over them, if specified.
/// This description is absent in GraphQL schema.
fn id(
& self,
// Renames the argument in GraphQL schema.
2020-11-14 07:58:04 -06:00
#[graphql(name = " myNum" )]
2020-10-06 05:18:31 -05:00
// Describes the argument in GraphQL schema.
2020-11-14 07:58:04 -06:00
#[graphql(description = " ID number of my own character." )]
2020-10-06 05:18:31 -05:00
// Specifies the default value for the argument.
// The concrete value may be omitted, and the `Default::default` one
// will be used in such case.
2020-11-14 07:58:04 -06:00
#[graphql(default = 5)]
2020-10-06 05:18:31 -05:00
num: i32,
) -> & str;
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
2021-08-11 09:45:17 -05:00
< p > Renaming policies for all < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > fields and arguments are supported as well:< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > #![allow(deprecated)]
< / span > < span class = "boring" > extern crate juniper;
< / span > use juniper::graphql_interface;
2021-08-11 09:45:17 -05:00
#[graphql_interface(rename_all = " none" )] // disables any renaming
trait Character {
// Now exposed as `my_id` and `my_num` in the schema
fn my_id(& self, my_num: i32) -> & str;
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
< h3 id = "custom-context" > < a class = "header" href = "#custom-context" > Custom context< / a > < / h3 >
2020-10-07 03:24:29 -05:00
< p > If a < a href = "https://docs.rs/juniper/0.14.2/juniper/trait.Context.html" > < code > Context< / code > < / a > is required in a trait method to resolve a < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > field, specify it as an argument.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > < span class = "boring" > use std::collections::HashMap;
< / span > use juniper::{graphql_interface, GraphQLObject};
2019-03-23 08:08:09 -05:00
struct Database {
humans: HashMap< String, Human> ,
}
impl juniper::Context for Database {}
2020-10-06 05:18:31 -05:00
#[graphql_interface(for = Human)] // look, ma, context type is inferred! ＼ ／
trait Character { // while still can be specified via `Context = ...` attribute argument
// If a field argument is named `context` or `ctx`, it's automatically assumed
// as a context argument.
fn id(& self, context: & Database) -> Option< & str> ;
2019-03-23 08:08:09 -05:00
2020-10-06 05:18:31 -05:00
// Otherwise, you may mark it explicitly as a context argument.
2020-11-14 07:58:04 -06:00
fn name(& self, #[graphql(context)] db: & Database) -> Option< & str> ;
2019-03-23 08:08:09 -05:00
}
2020-10-06 05:18:31 -05:00
#[derive(GraphQLObject)]
#[graphql(impl = CharacterValue, Context = Database)]
struct Human {
id: String,
name: String,
2019-03-23 08:08:09 -05:00
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
< h3 id = "using-executor-and-explicit-generic-scalar" > < a class = "header" href = "#using-executor-and-explicit-generic-scalar" > Using executor and explicit generic scalar< / a > < / h3 >
2020-10-07 03:24:29 -05:00
< p > If an < a href = "https://docs.rs/juniper/latest/juniper/struct.Executor.html" > < code > Executor< / code > < / a > is required in a trait method to resolve a < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > field, specify it as an argument.< / p >
2022-02-24 09:16:21 -06:00
< p > This requires to explicitly parametrize over < a href = "https://docs.rs/juniper/latest/juniper/trait.ScalarValue.html" > < code > ScalarValue< / code > < / a > , as < a href = "https://docs.rs/juniper/latest/juniper/struct.Executor.html" > < code > Executor< / code > < / a > does so. < / p >
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::{graphql_interface, graphql_object, Executor, LookAheadMethods as _, ScalarValue};
2020-10-06 05:18:31 -05:00
2020-10-07 03:24:29 -05:00
#[graphql_interface(for = Human, Scalar = S)] // notice specifying `ScalarValue` as existing type parameter
2020-10-06 05:18:31 -05:00
trait Character< S: ScalarValue> {
// If a field argument is named `executor`, it's automatically assumed
// as an executor argument.
2022-01-26 13:02:03 -06:00
fn id< 'a> (& self, executor: & 'a Executor< '_, '_, (), S> ) -> & 'a str;
2020-10-06 05:18:31 -05:00
// Otherwise, you may mark it explicitly as an executor argument.
2022-01-26 13:02:03 -06:00
fn name< 'b> (
2020-10-06 05:18:31 -05:00
& 'b self,
2020-11-14 07:58:04 -06:00
#[graphql(executor)] another: & Executor< '_, '_, (), S> ,
2022-01-26 13:02:03 -06:00
) -> & 'b str;
fn home_planet(& self) -> & str;
2020-10-06 05:18:31 -05:00
}
2019-03-23 08:08:09 -05:00
struct Human {
id: String,
2020-10-06 05:18:31 -05:00
name: String,
2022-01-26 13:02:03 -06:00
home_planet: String,
2019-03-23 08:08:09 -05:00
}
2022-01-26 13:02:03 -06:00
#[graphql_object(scalar = S: ScalarValue, impl = CharacterValue< S> )]
impl Human {
async fn id< 'a, S> (& self, executor: & 'a Executor< '_, '_, (), S> ) -> & 'a str
2020-10-06 05:18:31 -05:00
where
2022-01-26 13:02:03 -06:00
S: ScalarValue,
2020-10-06 05:18:31 -05:00
{
executor.look_ahead().field_name()
}
2019-03-23 08:08:09 -05:00
2022-01-26 13:02:03 -06:00
async fn name< 'b, S> (& 'b self, #[graphql(executor)] _: & Executor< '_, '_, (), S> ) -> & 'b str {
2020-10-06 05:18:31 -05:00
& self.name
}
2022-01-26 13:02:03 -06:00
fn home_planet< 'c, S> (& 'c self, #[graphql(executor)] _: & Executor< '_, '_, (), S> ) -> & 'c str {
// Executor may not be present on the trait method ^^^^^^^^^^^^^^^^^^^^^^^^
& self.home_planet
2019-03-23 08:08:09 -05:00
}
2020-10-06 05:18:31 -05:00
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
< h2 id = "scalarvalue-considerations" > < a class = "header" href = "#scalarvalue-considerations" > < code > ScalarValue< / code > considerations< / a > < / h2 >
2020-10-06 05:18:31 -05:00
< p > By default, < code > #[graphql_interface]< / code > macro generates code, which is generic over a < a href = "https://docs.rs/juniper/latest/juniper/trait.ScalarValue.html" > < code > ScalarValue< / code > < / a > type. This may introduce a problem when at least one of < a href = "https://spec.graphql.org/June2018/#sec-Interfaces" > GraphQL interface< / a > implementers is restricted to a concrete < a href = "https://docs.rs/juniper/latest/juniper/trait.ScalarValue.html" > < code > ScalarValue< / code > < / a > type in its implementation. To resolve such problem, a concrete < a href = "https://docs.rs/juniper/latest/juniper/trait.ScalarValue.html" > < code > ScalarValue< / code > < / a > type should be specified.< / p >
2022-02-24 09:16:21 -06:00
< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > extern crate juniper;
< / span > use juniper::{graphql_interface, DefaultScalarValue, GraphQLObject};
2020-10-06 05:18:31 -05:00
#[graphql_interface(for = [Human, Droid])]
2020-11-14 07:58:04 -06:00
#[graphql_interface(scalar = DefaultScalarValue)] // removing this line will fail compilation
2020-10-06 05:18:31 -05:00
trait Character {
fn id(& self) -> & str;
}
#[derive(GraphQLObject)]
2020-10-07 03:24:29 -05:00
#[graphql(impl = CharacterValue, Scalar = DefaultScalarValue)]
2019-03-23 08:08:09 -05:00
struct Human {
id: String,
home_planet: String,
}
2020-10-06 05:18:31 -05:00
#[derive(GraphQLObject)]
2020-10-07 03:24:29 -05:00
#[graphql(impl = CharacterValue, Scalar = DefaultScalarValue)]
2019-03-23 08:08:09 -05:00
struct Droid {
id: String,
primary_function: String,
}
2022-02-24 09:16:21 -06:00
< span class = "boring" >
< / span > < span class = "boring" > fn main() {}
< / span > < / code > < / pre > < / pre >
2019-03-23 08:08:09 -05:00
< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
2021-09-25 23:31:16 -05:00
< a rel = "prev" href = "../types/enums.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 >
2021-09-25 23:31:16 -05:00
< a rel = "next" href = "../types/input_objects.html" class = "mobile-nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
2019-03-23 08:08:09 -05:00
< i class = "fa fa-angle-right" > < / i >
< / a >
< div style = "clear: both" > < / div >
< / nav >
< / div >
< / div >
< nav class = "nav-wide-wrapper" aria-label = "Page navigation" >
2022-02-24 09:16:21 -06:00
< a rel = "prev" href = "../types/enums.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 >
2022-02-24 09:16:21 -06:00
< a rel = "next" href = "../types/input_objects.html" class = "nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
2019-03-23 08:08:09 -05:00
< 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 >
2022-02-24 09:16:21 -06:00
< script type = "text/javascript" >
window.playground_copyable = true;
< / script >
2021-09-25 23:31:16 -05:00
< script src = "../elasticlunr.min.js" type = "text/javascript" charset = "utf-8" > < / script >
2019-03-23 08:08:09 -05:00
< script src = "../mark.min.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "../searcher.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "../clipboard.min.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "../highlight.js" type = "text/javascript" charset = "utf-8" > < / script >
< script src = "../book.js" type = "text/javascript" charset = "utf-8" > < / script >
<!-- Custom JS scripts -->
< / body >
< / html >
