Update data-fetching.mdx

add GraphQL examples

Author: rderbier

modus/data-fetching.mdx

@@ -161,7 +161,7 @@ import { JSON } from "json-as"
 // the name of the Dgraph connection, as specified in the modus.json manifest
 const hostName: string = "my-dgraph"
 
-// Declare  classes used to parse the JSON document returned by Dgraph query.
+// Declare classes used to parse the JSON document returned by Dgraph query.
 @json
 class GetPersonResponse {
   persons: Person[] = []
@@ -314,38 +314,45 @@ import (
 // the name of the GraphQL connection, as specified in the modus.json manifest
 const hostName = "my-graphql-api"
 
+// Declare structures used to parse the JSON document returned by Dgraph query.
 type Person struct {
-  FirstName string `json:"firstName,omitempty"`
-  LastName  string `json:"lastName,omitempty"`
+  Name string    `json:"name,omitempty"`
+  Age  int32     `json:"age,omitempty"`
+  Home *Location `json:"home,omitempty"`
 }
 
-func QuerySpecificPerson(firstName, lastName string) (*Person, error) {
-  statement := `query queryPeople($firstName: String!, $lastName: String!) {
-    people: queryPerson(
-      first: 1,
-      filter: { firstName: { eq: $firstName }, lastName: { eq: $lastName } }
-    ) {
-      id
-      firstName
-      lastName
-    }
-  }`
+// Dgraph location predicates follow GeoJSON format
+type Location struct {
+  Latitude    float32   `json:"latitude,omitempty"`
+  Longitude   float32   `json:"longitude,omitempty"`
+}
+
+type GetPersonResponse struct {
+  Person *Person `json:"getPerson"`
+}
+
+func GetPerson(name string) (*Person, error) {
+  statement := `query getPerson($name: String!) {
+      getPerson(name: $name) {
+        age
+        name
+        home {
+          latitude
+          longitude
+        }
+      }
+    }`
 
   vars := map[string]any{
-    "firstName": firstName,
-    "lastName":  lastName,
+     "name": name,
   }
 
-  response, err := graphql.Execute[PeopleData](hostName, statement, vars)
+  response, err := graphql.Execute[GetPersonResponse](hostName, statement, vars)
   if err != nil {
     return nil, err
   }
 
-  if len(response.Data.People) == 0 {
-    return nil, nil // Person not found
-  }
-
-  return response.Data.People[0], nil
+  return response.Data.Person, nil
 }
 ```
 
@@ -355,37 +362,46 @@ import { graphql } from "@hypermode/modus-sdk-as"
 // the name of the GraphQL connection, as specified in the modus.json manifest
 const hostName: string = "my-graphql-api"
 
+// Declare  classes used to parse the JSON document returned by Dgraph query.
+@json
+class GetPersonResponse {
+  getPerson: Person
+}
+
 @json
 class Person {
-  id: string | null = null
-  firstName: string = ""
-  lastName: string = ""
+  name: string = ""
+  age: i32 = 0
+  home: Location
+}
+// Dgraph location predicates follow GeoJSON format
+@json
+class Location {
+  latitude: f64
+  longitude: f64
 }
 
-export function querySpecificPerson(firstName: string, lastName: string): Person | null {
-  const statement = `query queryPeople($firstName: String!, $lastName: String!) {
-    people: queryPerson(
-        first: 1,
-        filter: { firstName: { eq: $firstName }, lastName: { eq: $lastName } }
-    ) {
-        id
-        firstName
-        lastName
-    }
-  }`
+export function getPerson(name: string): Person | null {
+  const statement = `
+    query getPerson($name: String!) {
+      getPerson(name: $name) {
+        age
+        name
+        home {
+          latitude
+          longitude
+        }
+      }
+    }`
 
   const vars = new graphql.Variables()
-  vars.set("firstName", firstName)
-  vars.set("lastName", lastName)
+  vars.set("name", name)
 
-  const response = graphql.execute<PeopleData>(hostName, statement, vars)
+  const response = graphql.execute<GetPersonResponse>(hostName, statement, vars)
 
   if (!response.data) return null
 
-  const people = response.data!.people
-
-  if (people.length === 0) return null
-  return people[0]
+  return response.data!.getPerson
 }
 ```