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Enjoy the dark art of sub-app in koa



var ap = require('koa-app-party');
var App1 = ap.extend(function() {
var App2 = ap.extend(function() {
var Root = ap.Container.extend(function() {
  this.mount('/foo', App1);
  this.mount('/bar', App2);

Namespace chaining

Namespace is a special container that can be shared across constructor calls of ap.App and koa contexts.

To inject dependencies into namespace, is used to create a app subclass and define its namespace.

To learn more about namespace, visit othiym23/node-continuation-local-storage.

var App ='myapp', function(ns) {
  ns.set('foo', 'bar');
  assert(ns.get('origin') === 'container');
var Container ='mycontaier', function(ns) {
  ns.set('origin', 'container');
  this.mount('foo', App);
  this.use(function*() {
    this.body = this.ns.get('foo');
  • a new context is created in the constructor call of every App
  • if an app is mounted onto a container, in the runtime, all middlewares of this app will be run in a context that are merged from both container and app itself.
  • namespace will be re-created in every request session and will be deserted after response

More examples can be found in test/


var ap = require('koa-app-party');



    Alias for

  • ap.extend

    Alais for ap.App.extend

  • ap.App

    Atomic app unit

  • ap.Container

    Container app. Useful for mounting multiple atomic apps.

App = ap.App

  • App.extend(configurator)

    Create a subclass from current App. A configurator function will be invoked during constructor call with app instance as current context and other arguments passed to the constructor.

  • App.extend(props)

    A plain object can be passed to extend the prototype of subclass. props.init will be called during constructor call. And a reference to super method (if any), is available as this.super.

  •, designer)

    Like App.extend, but designer will be run with the namespace instance as a single argument. designer is intended to modify the namespace during the constructor call.

  • App.create(options)

    Create a App instance with options.

var app = new App(options)

  • app.listen(port, callback)

    Startup http server at local port assigned by port, and run callback.

  • app.acceptServer(server, callback) -> Promise

    Before the call of server.listen(), the server instance is passed to this method to do everything you need. Return a promise to continue. Defaults to return a Promise.resolve(true).

  • app.inject(injector)

    Run injector with namespace and callback before server.listen. Ensure callback is run, or the server will never listen.

Container = ap.Container

Subclass of App. Following class methods work just like the one on App:

  • Container.create
  • Container.extend

var container = new ap.Container()

  • container.mount(prefix, app)

    Mount an app at location of prefix.


    info is an object describing the layout of this container, such as

      '/app1': App1,
      '/app2': App2
      '/': '/app1'

Subclassing notes

  • Container.prototype.acceptServer is pre-defined. You should call this method if you are writing an override version of acceptServer on a container.
  • Always run extend or design to create subclasses.