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Query and Mutation

After setting up our project, we're ready to create our Todo list and query it.

Create a Todo#

Let's create a Todo in our testable example. We do it by adding the following code to example_test.go:

func Example_Todo() {
// ...
task1, err := client.Todo.Create().Save(ctx)
if err != nil {
log.Fatalf("failed creating a todo: %v", err)
}
fmt.Println(task1)
// Output:
// Todo(id=1)
}

Running go test should pass successfully.

Add Fields To The Schema#

As you can see, our Todos are too boring as they contain only the ID field. Let's improve this example by adding multiple fields to the schema in todo/ent/schema/todo.go:

func (Todo) Fields() []ent.Field {
return []ent.Field{
field.Text("text").
NotEmpty(),
field.Time("created_at").
Default(time.Now).
Immutable(),
field.Enum("status").
Values("in_progress", "completed").
Default("in_progress"),
field.Int("priority").
Default(0),
}
}

After adding these fields, we need to run the code-generation as before:

go generate ./ent

As you may notice, all fields have a default value on creation except the text field, which must be provided by the user. Let's change our example_test.go to follow these changes:

func Example_Todo() {
// ...
task1, err := client.Todo.Create().SetText("Add GraphQL Example").Save(ctx)
if err != nil {
log.Fatalf("failed creating a todo: %v", err)
}
fmt.Printf("%d: %q\n", task1.ID, task1.Text)
task2, err := client.Todo.Create().SetText("Add Tracing Example").Save(ctx)
if err != nil {
log.Fatalf("failed creating a todo: %v", err)
}
fmt.Printf("%d: %q\n", task2.ID, task2.Text)
// Output:
// 1: "Add GraphQL Example"
// 2: "Add Tracing Example"
}

Wonderful! We created a schema in the database with 5 columns (id, text, created_at, status, priority) and created 2 items in our todo list, by inserting 2 rows to the table.

tutorial-todo-create

Add Edges To The Schema#

Let’s say we want to design our todo list so that an item can depend on another item. Therefore, we'll add a parent edge to each Todo item, to get the item it depends on, and a back-reference edge named children in order to get all items that depend on it.

Let's change our schema again in todo/ent/schema/todo.go:

func (Todo) Edges() []ent.Edge {
return []ent.Edge{
edge.To("parent", Todo.Type).
Unique().
From("children"),
}
}

After adding these edges, we need to run the code-generation as before:

go generate ./ent

Connect 2 Todos#

We continue our edges example, by updating the 2 todo items we just created. We define that item-2 ("Add Tracing Example") depends on item-1 ("Add GraphQL Example").

tutorial-todo-create

func Example_Todo() {
// ...
if err := task2.Update().SetParent(task1).Exec(ctx); err != nil {
log.Fatalf("failed connecting todo2 to its parent: %v", err)
}
// Output:
// 1: "Add GraphQL Example"
// 2: "Add Tracing Example"
}

Query Todos#

After connecting item-2 to item-1, we're ready to start querying our todo list.

Query all todo items:#

func Example_Todo() {
// ...
// Query all todo items.
items, err := client.Todo.Query().All(ctx)
if err != nil {
log.Fatalf("failed querying todos: %v", err)
}
for _, t := range items {
fmt.Printf("%d: %q\n", t.ID, t.Text)
}
// Output:
// 1: "Add GraphQL Example"
// 2: "Add Tracing Example"
}

Query all todo items that depend on other items:#

func Example_Todo() {
// ...
// Query all todo items that depend on other items.
items, err := client.Todo.Query().Where(todo.HasParent()).All(ctx)
if err != nil {
log.Fatalf("failed querying todos: %v", err)
}
for _, t := range items {
fmt.Printf("%d: %q\n", t.ID, t.Text)
}
// Output:
// 2: "Add Tracing Example"
}

Query all todo items that don't depend on other items and have items that depend on them:#

func Example_Todo() {
// ...
// Query all todo items that don't depend on other items and have items that depend them.
items, err := client.Todo.Query().
Where(
todo.Not(
todo.HasParent(),
),
todo.HasChildren(),
).
All(ctx)
if err != nil {
log.Fatalf("failed querying todos: %v", err)
}
for _, t := range items {
fmt.Printf("%d: %q\n", t.ID, t.Text)
}
// Output:
// 1: "Add GraphQL Example"
}

Query parent through its children:#

func Example_Todo() {
// ...
// Get a parent item through its children and expect the
// query to return exactly one item.
parent, err := client.Todo.Query(). // Query all todos.
Where(todo.HasParent()). // Filter only those with parents.
QueryParent(). // Continue traversals to the parents.
Only(ctx) // Expect exactly one item.
if err != nil {
log.Fatalf("failed querying todos: %v", err)
}
fmt.Printf("%d: %q\n", parent.ID, parent.Text)
// Output:
// 1: "Add GraphQL Example"
}