easy-app

easy-app

Easy-app is a container for applications. It allows seamless linking of different parts together in a maner similar to AMD require system. Unlike AMD it's not just about static dependencies but is also capable to link things from various runtime levels. It also facilitates composing of app from small independent pieces.

Tasks

var App = require('easy-app')
var app = App()

app.set('bar', 10)

app.def('baz', function (bar) {
  return bar * 2
})

app.def('foo', function (bar, baz) {
  return bar + baz
})

The .def method defines what is called task. Once the task and all it's dependencies were defined we can evaluate it:

app.eval('foo', function (err, foo) {
  foo.should.equal(30)
})

Task may be async

app.def('config', function (done) {
  fs.readFile('config', done)
})

So done is a special case name meaning node style callback.

You can also define dependencies explicitly:

app.def('foo', ['bar', 'baz'], function (bar, baz) {
  return bar + baz
})

Composition

For big applications definition of everything in a single global container is a bad choice. In fact we want to compose such application from small loosely coupled pieces with very few things in common. No problem:

var subapp = App() // subapp is a normal app

// define tasks as usual
// Note that we are using short names like `req`.
// Not http_request, approval_request, etc
subapp.def('req', function (bar, baz) {})

// Specify missing tasks.
subapp.importing( // currently noop
  'bar',
  'baz'
)

Now we are ready to plug it in a global container:

app.install('super', subapp)

The above operation just copies everything from subapp to global container with all names been prefixed with super_. So our req task turned into

app.def('super_req', ['super_bar', 'super_baz'], function (bar, baz) {})

After (or before) installation we supposed to define missing super_bar and super_baz. If they are global shared dependencies it's better to do that via aliasing:

app
.def('bar', bar)
.def('baz', baz)

app
.install('super', subapp)
.alias('bar', 'super_bar')
.alias('baz', 'super_baz')
// or alternatively
app.install('super', subapp, {
  'bar': 'bar',
  'baz': '*' // shortcut for 'baz':'baz'
})

Layers

Almost always we have to deal with multiple runtime levels. For web applications they are typically "app" and "request". That's how we do that:

app.layer('app') // mark current instance to be app level
app.at('app', function () {
  app.def('config', function (done) {
    readJson('config.json', done)
  })
  app.def('db', function (config) {
    return require('monk')(config.connection_string)
  })
})
app.at('request', function () {
  app.def('session', function (db, req, done) {
    db.loadSession(req.cookie.session, done)
  })
  app.def('user', function (db, session, done) {
    db.loadUser(session.username, done)
  })
})
// ...
http.createServer(function (req, res) {
  app
  .run() // create next level instance
  .layer('request')
  .set('req', req) // seed
  .set('res', res)
  .eval('some task')
})

.at('request'), .layer('request') stuff is not really necessary for the above example.

Another way to attach task to a certain level is:

app.def('level', 'task', function (a, b) {})

Misc

Error handling

All task errors both sync and async are catched. In addition err.task property is set to the name of task which throwed an error.

Control flow

All tasks are executed sequentally one after another

eval

There is another special case dependency called eval. No surprise that it is similar to app.eval() but can be used within task and works for subapp case as expected.

app
.def('bar', bar)
.def('baz', baz)
.def('exec', function (task, eval, done) {
  eval(task, done)
})
app.run().set('task', 'bar').eval('exec') // bar executed

global
.instal('super', app)
.set('super_task', 'baz')
.eval('super_exec') // super_baz (i.e baz) executed

.use()

Useful for plugins

app.use(function plugin (container, param) {
  container.should.equal(app)
  this.should.equal(app)
  param.should.equal(10)
}, 10)

Installation

via npm

npm install easy-app

Related

Special thanks

This work intially inspired by The-Kiln

make-flow

make-flow is a util with similar ideas but intended to be just a simple control flow util rather than a full blown container.

License

(The MIT License)

Copyright (c) 2013 Eldar Gabdullin [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.