application.md

Application

$ npm install feathers --save

The core feathers module provides the ability to initialize new Feathers application instances. Each instance allows for registration and retrieval of services, plugin configuration, and getting and setting global configuration options. An initialized Feathers application is referred to as the app object. The API documented on this page works both, on the server and the client.

// To create a Feathers server application
const feathers = require('feathers');

// To create a client side application
const feathers = require('feathers/client');

const app = feathers();

Important: In addition to the API outlined below, a Feathers server application also provides the exact same functionality as an Express 4 application. For more advanced use of Feathers, familiarity with Express is highly recommended. For the interaction between Express and Feathers, also see the REST and Express chapters.

.use(path, service)

app.use(path, service) -> app allows registering a service object on the path.

// Add a service.
app.use('/messages', {
  get(id) {
    return Promise.resolve({
      id,
      text: `This is the ${name} message!`
    });
  }
});

On the server .use also provides the same functionality as Express app.use if passed something other than a service object (e.g. an Express middleware or other app object).

Important: REST services are registered in the same order as any other middleware. For additional information on how services and middleware interact see the Express chapter.

.service(path)

app.service(path) -> service returns the wrapped service object for the given path. Feathers internally creates a new object from each registered service. This means that the object returned by app.service(path) will provide the same methods and functionality as your original service object but also functionality added by Feathers and its plugins like service events and additional methods. path can be the service name with or without leading and trailing slashes.

const messageService = app.service('messages');

messageService.get('test').then(message => console.log(message));

app.use('/my/todos', {
  create(data) {
    return Promise.resolve(data);
  }
});

const todoService = app.service('my/todos');
// todoService is an event emitter
todoService.on('created', todo => 
  console.log('Created todo', todo)
);

.configure(callback)

app.configure(callback) -> app runs a callback function with the application as the context (this). It can be used to initialize plugins or services.

function setupService() {
  this.use('/todos', todoService);
}

app.configure(setupService);

.listen(port)

app.listen([port]) -> HTTPServer starts the application on the given port. It will first call the original Express app.listen([port]), then run app.setup(server) (see below) with the server object and then return the server object.

listen does nothing on the Feathers Client.

.setup(server)

app.setup(server) -> app is used to initialize all services by calling each services .setup(app, path) method (if available). It will also use the server instance passed (e.g. through http.createServer) to set up SocketIO (if enabled) and any other provider that might require the server instance.

Normally app.setup will be called automatically when starting the application via app.listen([port]) but there are cases when it needs to be called explicitly. For more information see the Express chapter.

.set(name, value)

app.set(name, value) -> app assigns setting name to value.

.get(name)

app.get(name) -> value retrieves the setting name. For more information on server side Express settings see the Express documentation.

app.set('port', 3030);

app.listen(app.get('port'));

.hooks(hooks)

app.hooks(hooks) -> app allows registration of application-level hooks. For more information see the application hooks section.

.on(eventname, listener)

Provided by the core NodeJS EventEmitter .on. Registers a listener method (function(data) {}) for the given eventname.

app.on('login', user => console.log('Logged in', user));

.emit(eventname, data)

Provided by the core NodeJS EventEmitter .emit. Emits the event eventname to all event listeners.

app.emit('myevent', {
  message: 'Something happened'
});

app.on('myevent', data => console.log('myevent happened', data));

.removeListener(eventname, [ listener ])

Provided by the core NodeJS EventEmitter .removeListener. Removes all or the given listener for eventname.