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SwagGen is a library and command line tool for parsing and generating code for OpenAPI/Swagger 3.0 specs, completely written in Swift.

Swagger 2 support has been removed. For Swagger 2 use version 3.0.2 or the swagger_2 branch

Swagger parser

It contains a Swagger library that can be used in Swift to load and parse Swagger specs.

Swagger code generator

SwagGen is command line tool that generates code from a OpenAPI/Swagger 3.0 spec. Templates for any language can be written that leverage this generator.

Swift template

SwagGen includes a bundled template for generating a client side Swift library for interfacing with the Swagger spec. It includes support for model inheritance, shared enums, discrete and mutable request objects, inline schemas, Codable and Equatable models, configurable options, generic networking stack, and many other niceties.


Make sure Xcode 11+ is installed first.

$ mint install yonaskolb/SwagGen


$ brew tap yonaskolb/SwagGen
$ brew install SwagGen


$ git clone
$ cd SwagGen
$ make install

Swift Package Manager

Use as CLI

$ git clone
$ cd swaggen
$ swift run

Use as dependency

Add the following to your Package.swift file's dependencies:

.package(url: "", from: "4.4.0"),

And then import wherever needed:

import SwagGenKit
import Swagger


Use --help to see usage information

swaggen --help
Usage: swaggen <command> [options]

  generate        Generates a template from a Swagger spec
  help            Prints this help information
  version         Prints the current version of this app


swaggen generate path_to_spec

Use swaggen generate --help to see the list of generation options.

  • spec: This is the path to the Swagger spec and is a required parameter. It can either be a file path or a web url to a YAML or JSON file

  • --language: The language to generate a template for. This defaults to swift for now.

  • --template:: This is the path to the template config yaml file. It can either be a direct path to the file, or a path to the parent directory which will by default look for /template.yml. If this is not passed, the default template for the language will be used.

  • --destination: The directory that the generated files will be added to.

  • --option: An option that will be merged with the template config options with those in this argument taking precedence, meaning any existing options of the same name will be overwritten. This argument can be repeated to pass in multiple options. Options must specify the option name and option value separated by a colon, with any spaces contained in quotes. Nested options in dictionaries can be set by using a dot syntax. The following formats are allowed:

    • -- option myOption:myValue
    • -- option modelSuffix: Model
    • -- option propertyNames.identifier: id
    • -- option "myOption: my value"
  • --clean: Controls if and how the destination directory is cleaned of non generated files. Options are:

    • none: no files are removed (default)
    • all: all other files are removed
    • leave.files: all files and directories except those that start with . in the destination directory are removed. This is useful for keeping configuration files and directories such as .git around, while still making sure that items removed from the spec are removed from the generated API.
  • --verbose: Show more verbose output

  • --silent: Silences any standard output. Errors will still be shown


swaggen generate --template Templates/Swift  --destination generated --option name:MyAPI --option "customProperty: custom value --clean leave.files"

For the Swift template, a handy option is name, which changes the name of the generated framework from the default of API. This can be set in the template or by passing in --option name:MyCoolAPI.

Swift Template

List of all available options:

name action expected values default value
name name of the API String API
authors authors in podspec String Yonas Kolb
baseURL baseURL in APIClient String first scheme, host, and base path of spec
fixedWidthIntegers whether to use types like Int32 and Int64 Bool false
homepage homepage in podspec String
modelPrefix model by adding a prefix and model file name String null
modelSuffix model by adding a suffix and model file name String null
mutableModels whether model properties are mutable Bool true
modelType whether each model is a struct or class String class
modelInheritance whether models use inheritance. Must be false for structs Bool true
modelNames override model names [String: String] [:]
modelProtocol customize protocol name that all models conform to String APIModel
enumNames override enum names [String: String] [:]
enumUndecodableCase whether to add undecodable case to enums Bool false
propertyNames override property names [String: String] [:]
safeArrayDecoding filter out invalid items in array instead of throwing Bool false
safeOptionalDecoding set invalid optionals to nil instead of throwing Bool false
tagPrefix prefix for all tags String null
tagSuffix suffix for all tags String null
codableResponses constrains all responses to be Codable Bool false
anyType override Any with custom type String Any
numberType override default number type when format not specified String Double

If writing your own Swift template there are a few types that are generated that you will need to provide typealias's for:

  • ID: The UUID format. Usually UUID or String
  • File: The file format. Usually URL, Data or a custom type with a mimeType and fileName
  • DateTime: The date-time format. Usually Date
  • DateDay: The date format. Usually Date or a custom type.


If you want to pass any required arguments when running in Xcode, you can edit the scheme to include launch arguments.


Templates are made up of a template config file, a bunch of Stencil files, and other files that will be copied over during generation

Template config

This is the configuration and manifest file for the template in YAML or JSON format. It can contain:

  • formatter: Optional formatter to use. This affects what properties are available in the templates and how they are formatted e.g. Swift
  • templateFiles: a list of template files. These can each have their paths, contents and destination directories modified through Stencil tags. One template file can also output to multiple files if they path is changed depending on a list context. Each file contains:
    • path: relative path to the template config. The extension is usually .stencil or the type it is going to end up as
    • context: optional context within the spec. This is provided to the generated file, otherwise the full context will be passed. If this is a list then a file will be created for each object and the context within that list is used. (e.g. a file for every model in the spec definitions gets it's own definition context). Note that properties in the template options field can be used here
    • destination: optional destination path. This can contain stencil tags whose context is that from the context above. e.g. if context was definitions then the path could be Models/{{ type }}.swift and the filename would be the type of the definition. If this is left out the destination will be the same as the path, relative to the final destination directory. If it resolves to an empty string it will be skipped and not generated.
  • copiedFiles: this is an array of relative paths that will be copied to the destination. They can be files or directories. This is used for files that won't have their contents, filenames or paths changed.
  • options: these are the options passed into every stencil file and can be used to customize the template. These options are merged with the options argument, with the argument options taking precendance. These options can be references in template file paths and their contents.

An example template for Swift can be found here

Template Files

These files follow the Stencil file format outlined here


Formatters change what information is available to the templates and how it's formatted. They can be specified via the formatter property in the template config. Usually these would map to a specific target language, but can be customized for different purposes.

Output Languages

SwagGen can be used to generate code for any language. At the moment there is only a formatter and template for Swift

Swift API usage

Usage documentation can be found in the Readme that is generated with your template.


This tool is powered by:

Thanks also to Logan Shire and his initial work on Swagger Parser



Pull requests and issues are welcome


SwagGen is licensed under the MIT license. See LICENSE for more info.