Additional support for turning Swift Types into OpenAPISchema

What's New

First stable release.


First stable release. Uses OpenAPIKit v2.

OpenAPI support

See parent library at


This library offers extended support for creating OpenAPI types from Swift types. Specifically, this library covers the subset of Swift types that require a JSONEncoder to either make an educated guess at the JSONSchema for the type or to turn arbitrary types into AnyCodable for use as schema examples or allowed values.


Dates will create different OpenAPI representations depending on the encoding settings of the JSONEncoder passed into the schema construction method.

// encoder1 has `.iso8601` `dateEncodingStrategy`
let schema = Date().dateOpenAPISchemaGuess(using: encoder1)
// ^ equivalent to:
let sameSchema = JSONSchema.string(
  format: .dateTime

// encoder2 has `.secondsSince1970` `dateEncodingStrategy`
let schema2 = Date().dateOpenAPISchemaGuess(using: encoder2)
// ^ equivalent to:
let sameSchema = JSONSchema.number(
  format: .double

It will even try to take a guess given a custom formatter date decoding strategy.


Swift enums produce schemas with allowed values specified as long as they conform to CaseIterable, Encodable, and AnyJSONCaseIterable (the last of which is free given the former two).

enum CodableEnum: String, CaseIterable, AnyJSONCaseIterable, Codable {
  case one
  case two

let schema = CodableEnum.caseIterableOpenAPISchemaGuess(using: JSONEncoder())
// ^ equivalent, although not equatable, to:
let sameSchema = JSONSchema.string(
  allowedValues: "one", "two"


Swift structs produce a best-guess schema as long as they conform to Sampleable and Encodable

struct Nested: Encodable, Sampleable {
  let string: String
  let array: [Int]

  // `Sampleable` just enables mirroring, although you could use it to produce
  // OpenAPI examples as well.
  static let sample: Self = .init(
    string: "",
    array: []

let schema = Nested.genericOpenAPISchemaGuess(using: JSONEncoder())
// ^ equivalent and indeed equatable to:
let sameSchema = JSONSchema.object(
  properties: [
    "string": .string,
    "array": .array(items: .integer)

Custom OpenAPI type representations

You can take the protocols offered by this library and OpenAPIKit and create arbitrarily complex OpenAPI types from your own Swift types. Right now, the only form of documentation on this subject is the fully realized example over in the JSONAPI+OpenAPI library. Just look for conformances to OpenAPISchemaType and OpenAPIEncodedSchemaType.


  • Swift Tools 5.2.0
View More Packages from this Author


Last updated: Thu Jun 30 2022 03:37:58 GMT-0500 (GMT-05:00)