ginga
v3.0.4
Published
Middleware framework for async functions using callback, promise or generator
Downloads
55
Readme
Ginga.js
Middleware based control flow for defining async JavaScript methods using callback, promise or generator.
npm install ginga
ginga([object])
Initialise ginga
var ginga = require('ginga')
var obj = ginga() //as a new object
var app = {}
ginga(app) //as a mixin
function App () { }
ginga(App.prototype) //as a prototype mixin
Method and Hook
app.define(name, [pre...], invoke)
Creates an async name
method that supports both callback and promise. See examples below.
app.use(name, [hook...])
Inject additional middleware between pre
and invoke
of method name
. See examples below.
Middleware
Middleware turns asynchronous functions into encapsulated, reusable set of building blocks. Upon calling a method, Ginga method goes through a sequence of middleware functions with following arguments:
ctx
- context event emitter object:- Maintains state throughout the method call, while encapsulated from
this
object. - A middleware can make changes to context object, or access changes made by previous middleware.
- Emits
end
event with error and result arguments.
- Maintains state throughout the method call, while encapsulated from
next
- optional stepping function using callback, which ends the sequence if callback with error argument.
Ginga middleware can be created using callback, promise or generator, interchangeably:
Callback
var ginga = require('ginga')
var app = ginga()
// define method
app.define('test', function (ctx, next) {
setTimeout(function () {
ctx.logs = ['pre']
next() // next middleware callback
}, 1000)
}, function (ctx) {
// not passing next argument: treated as synchronous call
ctx.logs.push('invoke')
return ctx.logs // returns value of the end of middleware sequence
})
// hook
app.use('test', function (ctx) {
ctx.logs.push('hook')
})
// method call with callback function
app.test(function (err, res) {
console.log(res) // ['pre', 'hook', 'invoke']
})
Promise
By returning promise, value will be resolved before passing to next middleware or returning result. Promise reject ends the middleware sequence.
var ginga = require('ginga')
var app = ginga()
// define method
app.define('test', function (ctx) {
return fnAsync().then(function (data) {
// do stuff
})
}, function (ctx) {
// returns result from last promise resolve
return fn2Async()
})
// method call with promise
app.test().then(...).catch(...)
Generator
In ES6 generators, functions can be paused and resumed using the yield
keyword.
Using caco, both promise and callback are 'yieldable' in ginga middleware.
This enables powerful control flow while maintaining compatibility.
var ginga = require('ginga')
var app = ginga()
app.define('test', function * (ctx, next) {
var foo = yield Promise.resolve('bar') // Promise is yieldable
yield setTimeout(next, 100) // callback based function is also yieldable
try {
ctx.key = yield fs.readfile('./foo/bar', next)
} catch (err) {
ctx.key = 'whatever'
}
}, function (ctx) * {
// returns result
return yield db.get(ctx.key)
})
ginga.params([param...])
Ginga built in ginga.params
middleware for parsing method arguments. Supports optional parameters and type-checking.
param
is string in form of
name[:type][?]
name
- name of parameter mapped from argumenttype
type checking (optional):string
,boolean
,function
,number
,date
,regexp
,object
,array
, case insensitive.?
- optional parameter.
var ginga = require('ginga')
var params = ginga.params
var app = ginga()
//define method with params parsing
app.define('test', params('a', 'b:number?', 'c:string?'), function (ctx) {
return ctx.params
})
//call method
app.test('s', 1, function (err, res) {
console.log(res) //{ a: 's', b: 1 }
})
app.test('s', 't', function (err, res) {
console.log(res) //{ a: 's', c: 't' }
})
app.test(function (err, res) {
console.log(err) //Error: Too few arguments. Expected at least 1
})
Plugin
app.use(plugin)
app.use
also accepts Ginga object as plugin. This will mount hooks into the main app.
var ginga = require('ginga')
//define app
var app = ginga()
app.define('test', function (ctx) {
ctx.logs = ['pre']
}, function (ctx) {
ctx.logs.push('invoke')
return ctx.logs
})
//define plugin
var plugin = ginga()
plugin.use('test', function (ctx, next) {
ctx.logs.push('plugin')
next()
})
//use plugin
app.use(plugin)
//call methods
app.test(function (err, res) {
console.log(res) //['pre','plugin', 'invoke']
})
Inheritance
By initialising Ginga with prototype mixin, hooks are also inherited in prototype chain:
var ginga = require('ginga')
function App () { }
var A = ginga(App.prototype) //ginga prototype mixin
A.define('test', function (ctx, next) {
ctx.logs = ['pre']
next()
}, function (ctx, done) {
ctx.logs.push('invoke')
done(null, ctx.logs)
})
var a1 = new App()
var a2 = new App()
//prototype hook
A.use('test', function (ctx) {
ctx.logs.push('A hook')
})
//instance hook
a1.use('test', function (ctx) {
ctx.logs.push('a1 hook')
})
a2.use('test', function (ctx) {
ctx.logs.push('a2 hook')
})
//call methods
a1.test(function (err, res) {
console.log(res) //['pre','A hook','a1 hook', 'invoke']
})
a2.test(function (err, res) {
console.log(res) //['pre','A hook','a2 hook', 'invoke']
})
License
MIT