Schema Definition

Prism’s GraphQL engine lets you define schemas entirely in Swift using a typed DSL. Every field, argument, and type is a first-class Swift value — you get compiler checks, autocomplete, and zero code generation.

Type System

GraphQL types map directly to PrismGraphQLType:

Available Types

.string       // GraphQL String
.int          // GraphQL Int
.float        // GraphQL Float
.boolean      // GraphQL Boolean
.id           // GraphQL ID
.nonNull(.string)          // String!
.list(.string)             // [String]
.list(.nonNull(.string))   // [String!]
.object("User")            // Custom object type
.enum("Status", ["ACTIVE", "INACTIVE"])  // Enum type
.input("CreateUserInput")  // Input type

Use .nonNull() to mark fields as required in your schema. Clients will get a validation error if a non-null field returns nil.

Defining Fields

Each field has a name, type, optional arguments, and a resolver function:

Field with Resolver

let nameField = PrismGraphQLField(
    name: "name",
    type: .nonNull(.string),
    args: [],
    description: "The user's full name",
    resolver: { info in
        let user = info.parentValue as? [String: Any]
        return user?["name"] as? String
    }
)

Fields with Arguments

Field with Arguments

let userField = PrismGraphQLField(
    name: "user",
    type: .object("User"),
    args: [
        PrismGraphQLArgument(name: "id", type: .nonNull(.id), description: "User ID")
    ],
    description: "Fetch a single user by ID",
    resolver: { info in
        let id = info.arguments["id"] as? String ?? ""
        return await UserService.find(id: id)
    }
)

Object Types

Group fields into object types:

User Type

let userType = PrismGraphQLObjectType(
    name: "User",
    fields: [
        "id": PrismGraphQLField(name: "id", type: .nonNull(.id), args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["id"]
        }),
        "name": PrismGraphQLField(name: "name", type: .nonNull(.string), args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["name"]
        }),
        "email": PrismGraphQLField(name: "email", type: .string, args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["email"]
        })
    ],
    description: "A registered user"
)

Building a Complete Schema

Define your types

Create object types for each entity in your domain.

Define the Query type

The Query type is the entry point for all read operations.

Define Mutation type (optional)

Mutations handle create, update, and delete operations.

Assemble the schema

Combine everything into a PrismGraphQLSchema.

Blog Schema Example

Complete Blog Schema

// Post type
let postType = PrismGraphQLObjectType(
    name: "Post",
    fields: [
        "id": PrismGraphQLField(name: "id", type: .nonNull(.id), args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["id"]
        }),
        "title": PrismGraphQLField(name: "title", type: .nonNull(.string), args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["title"]
        }),
        "body": PrismGraphQLField(name: "body", type: .string, args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["body"]
        }),
        "authorId": PrismGraphQLField(name: "authorId", type: .nonNull(.id), args: [], resolver: { info in
            (info.parentValue as? [String: Any])?["authorId"]
        })
    ]
)

// Query type — entry point
let queryType = PrismGraphQLObjectType(
    name: "Query",
    fields: [
        "posts": PrismGraphQLField(
            name: "posts",
            type: .list(.object("Post")),
            args: [],
            description: "List all posts",
            resolver: { _ in
                return [
                    ["id": "1", "title": "Hello Prism", "body": "Getting started...", "authorId": "1"],
                    ["id": "2", "title": "GraphQL in Swift", "body": "Native and fast...", "authorId": "1"]
                ]
            }
        ),
        "post": PrismGraphQLField(
            name: "post",
            type: .object("Post"),
            args: [PrismGraphQLArgument(name: "id", type: .nonNull(.id))],
            description: "Get a post by ID",
            resolver: { info in
                let id = info.arguments["id"] as? String
                // In reality, query your database here
                return ["id": id, "title": "Hello Prism", "body": "Content...", "authorId": "1"]
            }
        )
    ]
)

// Mutation type
let mutationType = PrismGraphQLObjectType(
    name: "Mutation",
    fields: [
        "createPost": PrismGraphQLField(
            name: "createPost",
            type: .object("Post"),
            args: [
                PrismGraphQLArgument(name: "title", type: .nonNull(.string)),
                PrismGraphQLArgument(name: "body", type: .string)
            ],
            resolver: { info in
                let title = info.arguments["title"] as? String ?? ""
                let body = info.arguments["body"] as? String
                // Save to database, return created post
                return ["id": UUID().uuidString, "title": title, "body": body, "authorId": "1"]
            }
        )
    ]
)

// Assemble schema
let schema = PrismGraphQLSchema(
    query: queryType,
    mutation: mutationType
)

The schema object is Sendable and can be shared across concurrent requests safely. Define it once at startup and pass it to your middleware.

Schema with Type Registry

For schemas with nested object types (e.g., a User that has Posts), register types in the schema so the executor can resolve nested selections:

Registering Types

var schema = PrismGraphQLSchema(query: queryType, mutation: mutationType)
schema.types["User"] = userType
schema.types["Post"] = postType
schema.types["Comment"] = commentType

Core

Middleware

Database

Real-Time

Content

Server Security

GraphQL

MCP

Infrastructure

Advanced

Testing

Schema Definition

Schema Definition

Type System

Defining Fields

Fields with Arguments

Object Types

Building a Complete Schema

Blog Schema Example

Schema with Type Registry

What’s Next

Queries

Mutations

​Schema Definition

​Type System

​Defining Fields

​Fields with Arguments

​Object Types

​Building a Complete Schema

​Blog Schema Example

​Schema with Type Registry

​What’s Next

Queries

Mutations

Schema Definition

Type System

Defining Fields

Fields with Arguments

Object Types

Building a Complete Schema

Blog Schema Example

Schema with Type Registry

What’s Next