choreo
Version:
A Robotics Framework
99 lines (78 loc) • 2.24 kB
JavaScript
/**
* Module dependencies
*/
var _ = require('lodash');
var async = require('async');
//
// TODO
// Pull this into a separate module, since it's not specific to Choreo.
//
/**
* Mix-in an `after` function to an EventEmitter.
*
* If `events` have already fired, trigger fn immediately (with no args)
* Otherwise bind a normal one-time event using
* `EventEmitter.prototype.once()`. Useful for checking whether or not
* something has finished loading, etc.
*
* This is a lot like jQuery's `$(document).ready()`.
*
* @param {EventEmitter} emitter
*/
module.exports = function mixinAfter(emitter) {
/**
* { emitter.warmEvents }
*
* Events which have occurred at least once
* (Required to support `emitter.after()`)
*/
emitter.warmEvents = {};
/**
* emitter.emit()
*
* Override `EventEmitter.prototype.emit`.
* (Required to support `emitter.after()`)
*/
var _emit = emitter.emit;
emitter.emit = function (evName) {
var args = Array.prototype.slice.call(arguments, 0);
emitter.warmEvents[evName] = true;
_emit.apply(emitter, args);
};
/**
* `emitter.after()`
*
* Fires your handler **IF THE SPECIFIED EVENT HAS ALREADY BEEN TRIGGERED**
* or **WHEN IT IS TRIGGERED**.
*
* @param {String|Array} events [name of the event(s)]
* @param {Function} fn [event handler function]
* @context {Choreo}
*/
emitter.after = function (events, fn) {
// Support a single event or an array of events
if (!_.isArray(events)) {
events = [events];
}
// Convert named event dependencies into an array
// of async-compatible functions.
var dependencies = _.reduce(events,
function (dependencies, event) {
var handlerFn = function (cb) {
if (emitter.warmEvents[event]) {
cb();
} else {
emitter.once(event, cb);
}
};
dependencies.push(handlerFn);
return dependencies;
}, []);
// When all events have fired, call `fn`
// (all arguments passed to `emit()` calls are discarded)
async.parallel(dependencies, function (err) {
if (err) choreo.log.error(err);
return fn();
});
};
};