Convert model schemata into Flow types (.js.flow)
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Convert swagger-style model schemata into Flow declaration files (.js.flow).


See the template for more details.

You can use your own custom template via the templatePath property, or your own template function via the templateFn property. See the Options below.

var jsonToFlow = require('json-to-flow');

// You can generate this yourself from tooling,
// or use the `definitions` property on a Swagger spec.
var schema = {
  User: {
    // primitives
    id: {type: 'number'},
    fullname: {type: 'string'},
    verified: {type: 'boolean'},
    // builtins
    created: {type: 'Date'},
    matcher: {type: 'RegExp'},

    // custom types
    childObj: {type: 'CustomType'},

    // arrays (uses swagger array spec)
    array: {
      type: 'array',
      items: {
        type: 'string' // could be a custom type or builtin too
    arrayModels: {
      type: 'array',
      items: {
        // will translate this into type: 'Pet'
        $ref:  '#/definitions/Pet'

    // Not part of swagger, but illustrating you can put anything in
    literal: {
      type: 'Promise<Array<Foo>>'
jsonToFlow(schema, {
  templateData: {
    modelSuperClass: 'Model',
    modelSuperClassPath: 'models/_model'
  targetPath: path.join(__dirname, 'models'),
  // templatePath: string, // Pass an optional abs ejs file path, or
  // templateFn: (data: {modelName: string, modelSchema: string,
  //                   modelSuperClass: string, ...options}) => string
}, function(err, results) {
  if (err) return console.error(err);


// (Shown with type and default value)
type JSONToFlowOptions = {

  // The path to the default template. You can override this. The entirety of the options
  // object is passed to the template so you can add anything you like.
  templatePath: string = path.join(__dirname, 'template.ejs'),

  // The default file extension. Note the leading `.`, intentional so you can add suffixes etc.
  templateExtension: string = '.js.flow',

  // This is populated at runtime with an ejs.compile() call. Replace this if you want to use another
  // template engine.
  templateFn: ?(data: Object) => string = void,

  // Optional hook for transforming data right before it is passed to templateFn.
  preTemplateFn: ?(data: Object) => Object = void,

  // By default, this translator takes in Swagger spec data and translates it to JS as closely
  // as is reasonable. You may not like how it does or may want to add your own hooks - do it here.
  // You can access the default translator at require('json-to-flow').defaults.translateField.
  translateField: (field: {type?: string, $ref?: string, format?: string}, options: JSONToFlowOptions) =>
    {type: string} = defaults.fieldTranslator,

  // If present, defines where the output goes. You can also pass a function.
  // If not present, will call back with compiled template.
  targetPath: ?(string | (modelName: string) => string) = void,

  // Variables used in default template.
  // Note that `modelName` and `modelSchema` is automatically merged into this on every iteration.
  templateData: Object = {
    // In default template, this is what the exported class extends
    modelSuperClass: string = 'Model',
    // In the default template, this is a map of types to add to the top of the file
    additionalTypes: Object = {},

Example Output

import {Model} from 'models/_model';

export class UserModel extends Model {
  id: number;
  fullname: string;
  verified: boolean;
  created: Date;
  matcher: RegExp;
  childObj: CustomType;
  array: Array<string>;
  arrayModels: Array<Pet>;
  literal: Promise<Array<Foo>>;