zero-roof-todo

zero-bus

There is a super event emitter class named Bus in zero core. This module will create a Bus instance and attach it to every request instance. You can use it via req.bus.

Usage

1. Add dependency to your module package.json file like:

{
	"name" : "YOUR_MODULE_NAME",
	"zero" : {
		"dependencies" : {
			"bus" : "^0.0.1"
		}
	}
}

2. Declare the event you want to listen in module.exports like:

module.exports = {
	listen : {
       'someEvent' : function eventHandler(/*arguments of fired event*/){

       }
    }
}

3. Or you can use it in router handler like code below, don't forget declare module dependency in package.json first.

module.exports = {
	route ： {
		'/route/:param' : function(req){
			req.bus.fire('someEvent', arg1, arg2)
		}
	}
}

Advanced Usage

Ordering listeners

You can specify the fire order of all listeners on certain event using:

bus.on({
	"event":'someEvent',
	"function":function handlerName(){},
	"module":"otherModule"
})

bus.on({
	"event":'someEvent',
	"function":function handler(){},
	"order":{before:"otherModule.handlerName"}, //make this handler triggered before the one above
	"module":"someModule"
})

sharing data through bus

You can use bus.data() to store and retrieve data.

bus.data('user',{id:1,name:'zero'}) //set data
bus.data('user') //retrieve data

//advanced usage
bus.data('user.id',2) //this will set the id of the object named `user` to 2, instead of creating a new piece of data named 'user.id'.

keeping trace stack of event

As you may know, bus can trace event stack in debug mode, but there are some basic rules you need to know first:

• If you fired another event synchronously(such as in a promise) in your event handler, you need to return a promise that holds the result of the event you fired. Mostly simply return bus.fire('someEvent')( the return value of bus.fire() is a promise) would just work.

• Returning bus.error() will stop all event processing immediately.

• Handlers on same event run synchronously, which means if you are doing something synchronously( such as connecting database ) in a event handler, other handlers attached on the same event won't wait, unless you return a promise with attribute block set to true.