ent/doc: o2m two types example

Reviewed By: idoshveki

Differential Revision: D17050002

fbshipit-source-id: 183c41bfb8cffb463a80a80590a01aba176e3b2a

examples/o2m2types/o2m2types.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/facebookincubator/ent/examples/o2m2types/ent"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func main() {
+	db, err := sql.Open("sqlite3", "file:o2o2types?mode=memory&cache=shared&_fk=1")
+	if err != nil {
+		log.Fatalf("failed opening connection to sqlite: %v", err)
+	}
+	defer db.Close()
+	client := ent.NewClient(ent.Driver(db))
+	ctx := context.Background()
+	// run the auto migration tool.
+	if err := client.Schema.Create(ctx); err != nil {
+		log.Fatalf("failed creating schema resources: %v", err)
+	}
+	if err := Do(ctx, client); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func Do(ctx context.Context, client *ent.Client) error {
+	// Create the 2 pets.
+	pedro, err := client.Pet.
+		Create().
+		SetName("pedro").
+		Save(ctx)
+	if err != nil {
+		return fmt.Errorf("creating pet: %v", err)
+	}
+	lola, err := client.Pet.
+		Create().
+		SetName("lola").
+		Save(ctx)
+	if err != nil {
+		return fmt.Errorf("creating pet: %v", err)
+	}
+	// Create the user, and add its pets on the creation.
+	a8m, err := client.User.
+		Create().
+		SetAge(30).
+		SetName("a8m").
+		AddPets(pedro, lola).
+		Save(ctx)
+	if err != nil {
+		return fmt.Errorf("creating user: %v", err)
+	}
+	fmt.Println("User created:", a8m)
+	// Output: User(id=1, age=30, name=a8m)
+
+	// Query the owner. Unlike `Only`, `OnlyX` panics if an error occurs.
+	owner := pedro.QueryOwner().OnlyX(ctx)
+	fmt.Println(owner.Name)
+	// Output: a8m
+
+	// Traverse the sub-graph. Unlike `Count`, `CountX` panics if an error occurs.
+	count := pedro.
+		QueryOwner(). // a8m
+		QueryPets().  // pedro, lola
+		CountX(ctx)   // count
+	fmt.Println(count)
+	// Output: 2
+	return nil
+}