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<ol class="chapter"><li class="chapter-item expanded "><a href="../warpgrapher/intro.html"><strong aria-hidden="true">1.</strong> Warpgrapher</a></li><li class="chapter-item expanded "><a href="../warpgrapher/quickstart.html"><strong aria-hidden="true">2.</strong> Quickstart</a></li><li class="chapter-item expanded "><a href="../integrations/intro.html"><strong aria-hidden="true">3.</strong> Server Integration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../integrations/actix.html"><strong aria-hidden="true">3.1.</strong> Actix Web</a></li><li class="chapter-item expanded "><a href="../integrations/lambda.html"><strong aria-hidden="true">3.2.</strong> AWS Lambda</a></li></ol></li><li class="chapter-item expanded "><a href="../configuration/intro.html"><strong aria-hidden="true">4.</strong> Configuration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../configuration/databases.html"><strong aria-hidden="true">4.1.</strong> Databases</a></li><li class="chapter-item expanded "><a href="../configuration/formats.html"><strong aria-hidden="true">4.2.</strong> Formats</a></li><li class="chapter-item expanded "><a href="../configuration/types.html"><strong aria-hidden="true">4.3.</strong> Types</a></li><li class="chapter-item expanded "><a href="../configuration/relationships.html"><strong aria-hidden="true">4.4.</strong> Relationships</a></li></ol></li><li class="chapter-item expanded "><a href="../api/intro.html"><strong aria-hidden="true">5.</strong> CRUD API Usage Examples</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../api/node_create.html"><strong aria-hidden="true">5.1.</strong> Node Create</a></li><li class="chapter-item expanded "><a href="../api/node_read.html"><strong aria-hidden="true">5.2.</strong> Node Read</a></li><li class="chapter-item expanded "><a href="../api/node_update.html"><strong aria-hidden="true">5.3.</strong> Node Update</a></li><li class="chapter-item expanded "><a href="../api/node_delete.html"><strong aria-hidden="true">5.4.</strong> Node Delete</a></li><li class="chapter-item expanded "><a href="../api/rel_create.html"><strong aria-hidden="true">5.5.</strong> Relationship Create</a></li><li class="chapter-item expanded "><a href="../api/rel_read.html"><strong aria-hidden="true">5.6.</strong> Relationship Read</a></li><li class="chapter-item expanded "><a href="../api/rel_update.html"><strong aria-hidden="true">5.7.</strong> Relationship Update</a></li><li class="chapter-item expanded "><a href="../api/rel_delete.html"><strong aria-hidden="true">5.8.</strong> Relationship Delete</a></li></ol></li><li class="chapter-item expanded "><a href="../engine/intro.html"><strong aria-hidden="true">6.</strong> Engine Features</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../engine/endpoints_static.html"><strong aria-hidden="true">6.1.</strong> Static Endpoints</a></li><li class="chapter-item expanded "><a href="../engine/endpoints_defined.html"><strong aria-hidden="true">6.2.</strong> Defined Endpoints</a></li><li class="chapter-item expanded "><a href="../engine/dynamic_props.html" class="active"><strong aria-hidden="true">6.3.</strong> Dynamic Props</a></li><li class="chapter-item expanded "><a href="../engine/dynamic_rels.html"><strong aria-hidden="true">6.4.</strong> Dynamic Relationships</a></li><li class="chapter-item expanded "><a href="../engine/context_request.html"><strong aria-hidden="true">6.5.</strong> Request Context</a></li><li class="chapter-item expanded "><a href="../engine/input_validation.html"><strong aria-hidden="true">6.6.</strong> Input Validation</a></li><li class="chapter-item expanded "><a href="../engine/event_handlers.html"><strong aria-hidden="true">6.7.</strong> Event Handlers</a></li></ol></li></ol>
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<h1 id="dynamic-props"><a class="header" href="#dynamic-props">Dynamic Props</a></h1>
<p>When Warpgrapher auto-generates a CRUD endpoint, the values of Node and Relationship properties are retreived from the database and returned in a query. In some cases, however, it may be necessary to perform real-time computations to derive the value of a prop. We call these type of properties "dynamic properties", and Warpgrapher provides a mechanism to execute custom logic to resolve their values.</p>
<h2 id="configuration"><a class="header" href="#configuration">Configuration</a></h2>
<p>In the configuration below, <code>points</code> is a dynamic property on the <code>Project</code> type. It has an associated resolver name of <code>resolve_project_points</code>. That name will be used later to connect the Rust resolver function to this entry in the configuration.</p>
<pre><code class="language-rust no_run noplayground">model:
- name: Project
props:
- name: name
type: String
- name: points
type: Int
resolver: resolve_project_points
";
</code></pre>
<h2 id="implementation"><a class="header" href="#implementation">Implementation</a></h2>
<p>The implementation below defines the resolver. In this example, the resolver simply returns a constant value. In a real system, the implementation might retrieve records and do some calculation to total up a number of points associated with a project.</p>
<pre><code class="language-rust no_run noplayground">fn resolve_project_points(facade: ResolverFacade<AppRequestContext>) -> BoxFuture<ExecutionResult> {
Box::pin(async move {
// compute value
let points = 5;
facade.resolve_scalar(points)
})
}
</code></pre>
<h2 id="add-resolvers-to-the-engine"><a class="header" href="#add-resolvers-to-the-engine">Add Resolvers to the Engine</a></h2>
<p>The code in the snippet below adds the resolver function to a map. They key is the name for the custom resolver that was used in the configuration, above. The map is then passed to the Wargrapher engine, allowing the engine to find the resolver function when the dynamic property must be resolved.</p>
<pre><code class="language-rust no_run noplayground"> let mut resolvers = Resolvers::<AppRequestContext>::new();
resolvers.insert(
"resolve_project_points".to_string(),
Box::new(resolve_project_points),
);
// create warpgrapher engine
let engine: Engine<AppRequestContext> = Engine::new(config, db)
.with_resolvers(resolvers)
.build()
.expect("Failed to build engine");
</code></pre>
<h2 id="example-api-call"><a class="header" href="#example-api-call">Example API Call</a></h2>
<p>The following GraphQL query uses the dynamic resolver defined above.</p>
<pre><code class="language-rust no_run noplayground"> // create new project
let query = "
mutation {
ProjectCreate(input: {
name: \"Project1\"
}) {
id
points
}
}
"
.to_string();
let metadata = HashMap::new();
let result = engine.execute(query, None, metadata).await.unwrap();
</code></pre>
<h2 id="full-example-source"><a class="header" href="#full-example-source">Full Example Source</a></h2>
<p>See below for the full source code to the example above.</p>
<pre><code class="language-rust no_run noplayground">use std::collections::HashMap;
use std::convert::TryFrom;
use warpgrapher::engine::config::Configuration;
use warpgrapher::engine::context::RequestContext;
use warpgrapher::engine::database::cypher::CypherEndpoint;
use warpgrapher::engine::database::DatabaseEndpoint;
use warpgrapher::engine::resolvers::{ExecutionResult, ResolverFacade, Resolvers};
use warpgrapher::juniper::BoxFuture;
use warpgrapher::Engine;
static CONFIG: &str = "
version: 1
model:
- name: Project
props:
- name: name
type: String
- name: points
type: Int
resolver: resolve_project_points
";
#[derive(Clone, Debug)]
struct AppRequestContext {}
impl RequestContext for AppRequestContext {
type DBEndpointType = CypherEndpoint;
fn new() -> AppRequestContext {
AppRequestContext {}
}
}
fn resolve_project_points(facade: ResolverFacade<AppRequestContext>) -> BoxFuture<ExecutionResult> {
Box::pin(async move {
// compute value
let points = 5;
facade.resolve_scalar(points)
})
}
#[tokio::main]
async fn main() {
// parse warpgrapher config
let config = Configuration::try_from(CONFIG.to_string()).expect("Failed to parse CONFIG");
// define database endpoint
let db = CypherEndpoint::from_env()
.expect("Failed to parse cypher endpoint from environment")
.pool()
.await
.expect("Failed to create cypher database pool");
// define resolvers
let mut resolvers = Resolvers::<AppRequestContext>::new();
resolvers.insert(
"resolve_project_points".to_string(),
Box::new(resolve_project_points),
);
// create warpgrapher engine
let engine: Engine<AppRequestContext> = Engine::new(config, db)
.with_resolvers(resolvers)
.build()
.expect("Failed to build engine");
// create new project
let query = "
mutation {
ProjectCreate(input: {
name: \"Project1\"
}) {
id
points
}
}
"
.to_string();
let metadata = HashMap::new();
let result = engine.execute(query, None, metadata).await.unwrap();
// verify result
assert_eq!(
"123456",
result
.get("data")
.unwrap()
.get("GetEnvironment")
.unwrap()
.as_str()
.unwrap(),
);
}
</code></pre>
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