# Nested Mutations

Lighthouse allows you to create, update or delete models and their associated relationships, all in one single mutation. This is enabled by the nested arg resolvers mechanism.

# Return Types Required

You have to define return types on your relationship methods so that Lighthouse can detect them.

use Illuminate\Database\Eloquent\Relations\BelongsTo;

class Post extends Model
{
    public function user(): BelongsTo // WORKS
    {
        return $this->belongsTo(User::class);
    }

    public function comments() // DOES NOT WORK
    {
        return $this->hasMany(Comment::class);
    }
}

# Partial Failure

By default, all mutations are wrapped in a database transaction. If any of the nested operations fail, the whole mutation is aborted and no changes are written to the database.

You can change this setting in the configuration.

# Polymorphic Relation Limitations

Because the GraphQL Specification does not support polymorphic Input types (yet), the available functionality is limited.

It is not possible to have an argument that can contain different types, which would be necessary to pass the attributes the different related models might have. For now, we can only support cases where the input type does not change across related models, e.g. connecting through an ID, disconnecting or deleting the relation.

See this issue (opens new window) for further discussion.

# BelongsTo

We will start of by defining a mutation to create a post.

type Mutation {
  createPost(input: CreatePostInput! @spread): Post @create
}

The mutation takes a single argument input that contains data about the Post you want to create.

input CreatePostInput {
  title: String!
  author: CreateUserBelongsTo
}

The first argument title is a value of the Post itself and corresponds to a column in the database.

The second argument author is named just like the relationship method that is defined on the Post model. A nested BelongsTo relationship exposes the following operations:

  • connect it to an existing model
  • create a new related model and attach it
  • update an existing model and attach it
  • upsert a new or an existing model and attach it
  • disconnect the related model
  • delete the related model and the association to it

Both disconnect and delete don't make much sense in the context of an update. You can control what operations are possible by defining just what you need in the input. We choose to expose the following operations on the related User model:

input CreateUserBelongsTo {
  connect: ID
  create: CreateUserInput
  update: UpdateUserInput
  upsert: UpsertUserInput
}

Finally, you need to define the input that allows you to create a new User.

input CreateUserInput {
  name: String!
}

To create a new model and connect it to an existing model, just pass the ID of the model you want to associate.

mutation {
  createPost(input: { title: "My new Post", author: { connect: 123 } }) {
    id
    author {
      name
    }
  }
}

Lighthouse will create a new Post and associate an User with it.

{
  "data": {
    "createPost": {
      "id": 456,
      "author": {
        "name": "Herbert"
      }
    }
  }
}

If the related model does not exist yet, you can also create a new one.

mutation {
  createPost(
    input: { title: "My new Post", author: { create: { name: "Gina" } } }
  ) {
    id
    author {
      id
    }
  }
}
{
  "data": {
    "createPost": {
      "id": 456,
      "author": {
        "id": 55
      }
    }
  }
}

When issuing an update, you can also allow the user to remove a relation. Both disconnect and delete remove the association to the author, but delete also removes the author model itself.

type Mutation {
  updatePost(input: UpdatePostInput! @spread): Post @update
}

input UpdatePostInput {
  id: ID!
  title: String
  author: UpdateUserBelongsTo
}

input UpdateUserBelongsTo {
  connect: ID
  create: CreateUserInput
  update: UpdateUserInput
  upsert: UpdateUserInput
  disconnect: Boolean
  delete: Boolean
}

You must pass a truthy value to disconnect and delete for them to actually run. This structure was chosen as it is consistent with updating BelongsToMany relationships and allows the query string to be mostly static, taking a variable value to control its behaviour.

mutation UpdatePost($disconnectAuthor: Boolean) {
  updatePost(
    input: {
      id: 1
      title: "An updated title"
      author: { disconnect: $disconnectAuthor }
    }
  ) {
    title
    author {
      name
    }
  }
}

The author relationship will only be disconnected if the value of the variable $disconnectAuthor is true, if false or null are passed, it will not change.

{
  "data": {
    "updatePost": {
      "id": 1,
      "title": "An updated title",
      "author": null
    }
  }
}

When issuing an upsert, you may expose the same nested operations as an update. In case a new model is created, they will simply be ignored.

mutation UpdatePost($disconnectAuthor: Boolean) {
  upsertPost(
    input: {
      id: 1
      title: "An updated or created title"
      author: { disconnect: $disconnectAuthor }
    }
  ) {
    id
    title
    author {
      name
    }
  }
}
{
  "data": {
    "upsertPost": {
      "id": 1,
      "title": "An updated or created title",
      "author": null
    }
  }
}

# MorphTo

The basic structure of this nested mutation type is similar to BelongsTo, the main difference being that the connect operation requires an input type with both the id and type of the related model.

type Task {
  name: String
}

type Image {
  url: String
  imageable: Task @morphTo
}

type Mutation {
  updateImage(input: UpdateImageInput! @spread): Image @update
}

input UpdateImageInput {
  id: ID!
  url: String
  imageable: UpdateImageableMorphTo
}

input UpdateImageableMorphTo {
  connect: ConnectImageableInput
  disconnect: Boolean
  delete: Boolean
}

input ConnectImageableInput {
  type: String!
  id: ID!
}

You can use connect to associate existing models.

mutation {
  createImage(
    input: {
      url: "https://cats.example/cute"
      imageable: { connect: { type: "App\\Models\\Task", id: 1 } }
    }
  ) {
    id
    url
    imageable {
      id
      name
    }
  }
}

The disconnect operations allows you to detach the currently associated model.

mutation {
  updateImage(
    input: {
      id: 1
      url: "https://dogs.example/supercute"
      imageable: { disconnect: true }
    }
  ) {
    url
    imageable {
      id
      name
    }
  }
}

The delete operation both detaches and deletes the currently associated model.

mutation {
  upsertImage(
    input: {
      id: 1
      url: "https://bizniz.example/serious"
      imageable: { delete: true }
    }
  ) {
    url
    imageable {
      id
      name
    }
  }
}

# HasOne

The counterpart to a BelongsTo relationship can be HasOne. We will start off by defining a mutation to update a User.

type Mutation {
  updateUser(input: UpdateUserInput! @spread): User @update
}

This mutation takes a single argument input that contains values of the User itself and its associated Phone model.

input UpdateUserInput {
  id: ID!
  name: String
  phone: UpdatePhoneHasOne
}

Now, we can expose operations that allows us to update the users phone.

input UpdatePhoneHasOne {
  create: CreatePhoneInput
  update: UpdatePhoneInput
  upsert: UpsertPhoneInput
  delete: ID
}

input CreatePhoneInput {
  number: String!
}

input UpdatePhoneInput {
  id: ID!
  number: String
}

input UpsertPhoneInput {
  id: ID
  number: String
}

We can now update the User and their phone in one request.

mutation {
  updateUser(
    input: {
      id: 4
      name: "Donald"
      phone: { update: { id: 92, number: "+12 345 6789" } }
    }
  ) {
    id
  }
}

# MorphOne

Works exactly like HasOne

# HasMany

Another possible counterpart to a BelongsTo relationship is HasMany. We will start off by defining a mutation to create an User.

type Mutation {
  createUser(input: CreateUserInput! @spread): User @create
}

This mutation takes a single argument input that contains values of the User itself and its associated Post models.

input CreateUserInput {
  name: String!
  posts: CreatePostsHasMany
}

Now, we can expose an operation that allows us to directly create new posts right when we create the User.

input CreatePostsHasMany {
  create: [CreatePostInput!]!
}

input CreatePostInput {
  title: String!
}

We can now create a User and some posts with it in one request.

mutation {
  createUser(
    input: {
      name: "Phil"
      posts: {
        create: [
          { title: "Phils first post" }
          { title: "Awesome second post" }
        ]
      }
    }
  ) {
    id
    posts {
      id
    }
  }
}
{
  "data": {
    "createUser": {
      "id": 23,
      "posts": [
        {
          "id": 434
        },
        {
          "id": 435
        }
      ]
    }
  }
}

When updating a User, further nested operations become possible. It is up to you which ones you want to expose through the schema definition.

The following example covers the full range of possible operations:

type Mutation {
  updateUser(input: UpdateUserInput! @spread): User @update
}

input UpdateUserInput {
  id: ID!
  name: String
  posts: UpdatePostsHasMany
}

input UpdatePostsHasMany {
  create: [CreatePostInput!]
  update: [UpdatePostInput!]
  upsert: [UpsertPostInput!]
  delete: [ID!]
  connect: [ID!]
  disconnect: [ID!]
}

input CreatePostInput {
  title: String!
}

input UpdatePostInput {
  id: ID!
  title: String
}

input UpsertPostInput {
  id: ID!
  title: String
}
mutation {
  updateUser(
    input: {
      id: 3
      name: "Phillip"
      posts: {
        create: [{ title: "A new post" }]
        update: [{ id: 45, title: "This post is updated" }]
        delete: [8]
        connect: [1, 2, 3]
        disconnect: [6]
      }
    }
  ) {
    id
    posts {
      id
    }
  }
}

The behaviour for upsert is a mix between updating and creating, it will produce the needed action regardless of whether the model exists or not.

# MorphMany

Works exactly like Has Many.

# BelongsToMany

A belongs to many relation allows you to create new related models as well as attaching existing ones.

type Mutation {
  createPost(input: CreatePostInput! @spread): Post @create
}

input CreatePostInput {
  title: String!
  authors: CreateAuthorBelongsToMany
}

input CreateAuthorBelongsToMany {
  create: [CreateAuthorInput!]
  upsert: [UpsertAuthorInput!]
  connect: [ID!]
  sync: [ID!]
}

input CreateAuthorInput {
  name: String!
}

input UpsertAuthorInput {
  id: ID!
  name: String!
}

Just pass the ID of the models you want to associate or their full information to create a new relation.

mutation {
  createPost(
    input: {
      title: "My new Post"
      authors: {
        create: [{ name: "Herbert" }]
        upsert: [{ id: 2000, name: "Newton" }]
        connect: [123]
      }
    }
  ) {
    id
    authors {
      name
    }
  }
}

Lighthouse will detect the relationship and attach, update or create it.

{
  "data": {
    "createPost": {
      "id": 456,
      "authors": [
        {
          "id": 165,
          "name": "Herbert"
        },
        {
          "id": 2000,
          "name": "Newton"
        },
        {
          "id": 123,
          "name": "Franz"
        }
      ]
    }
  }
}

It is also possible to use the sync operation to ensure only the given IDs will be contained withing the relation.

mutation {
  createPost(input: { title: "My new Post", authors: { sync: [123] } }) {
    id
    authors {
      name
    }
  }
}

Updates on BelongsToMany relations may expose additional nested operations:

input UpdateAuthorBelongsToMany {
  create: [CreateAuthorInput!]
  connect: [ID!]
  update: [UpdateAuthorInput!]
  upsert: [UpsertAuthorInput!]
  sync: [ID!]
  syncWithoutDetaching: [ID!]
  delete: [ID!]
  disconnect: [ID!]
}

# Storing Pivot Data

It is common that many-to-many relations store some extra data in pivot tables. Suppose we want to track what movies a user has seen. In addition to connecting the two entities, we want to store how well they liked it:

type User {
  id: ID!
  seenMovies: [Movie!] @belongsToMany
}

type Movie {
  id: ID!
  pivot: UserMoviePivot
}

type UserMoviePivot {
  "How well did the user like the movie?"
  rating: String
}

Laravel's sync(), syncWithoutDetach() or connect() methods allow you to pass an array where the keys are IDs of related models and the values are pivot data.

Lighthouse exposes this capability through the nested operations on many-to-many relations. Instead of passing just a list of ids, you can define an input type that also contains pivot data. It must contain a field called id to contain the ID of the related model, all other fields will be inserted into the pivot table.

type Mutation {
  updateUser(input: UpdateUserInput! @spread): User @update
}

input UpdateUserInput {
  id: ID!
  seenMovies: UpdateUserSeenMovies
}

input UpdateUserSeenMovies {
  connect: [ConnectUserSeenMovie!]
}

input ConnectUserSeenMovie {
  id: ID!
  rating: String
}

You can now pass along pivot data when connecting users to movies:

mutation {
  updateUser(
    input: {
      id: 1
      seenMovies: { connect: [{ id: 6, rating: "A perfect 5/7" }, { id: 23 }] }
    }
  ) {
    id
    seenMovies {
      id
      pivot {
        rating
      }
    }
  }
}

You will get the following response:

{
  "data": {
    "updateUser": {
      "id": 1,
      "seenMovies": [
        {
          "id": 6,
          "pivot": {
            "rating": "A perfect 5/7"
          }
        },
        {
          "id": 20,
          "pivot": {
            "rating": null
          }
        }
      ]
    }
  }
}

It is also possible to use the sync and syncWithoutDetaching operations.

# MorphToMany

Works exactly like BelongsToMany.