var test = { }
$(test).on("testEvent", function (){
console.log("testEvent has fired");
});
$.event.trigger("testEvent");
I am trying to using jQuery to do a publish/subscribe mechanism using events. I need to be able to attach events to non-DOM objects and be able to have them all fire from a single global trigger. I expected the code above to work but it did not result in the testEvent firing for the test object.
Note that there will be multiple objects in which an event will be subscribed to. A single $.event.trigger should fire all of those events.
Do note that this code works fine:
$('#someID').on("testEvent", function () {
console.log('testEvent has fired from DOM element');
})
$.event.trigger("testEvent");
After doing some research it appears as though jQuery 1.7 provides an easy way to introduce a publish/subscribe mechanism. (found here) In order to have a publish/subscribe mechanism the following code can be used:
(function ($, window, undefined) {
var topics = {};
jQuery.Topic = function (id) {
var callbacks, method, topic = id && topics[id];
if (!topic) {
callbacks = jQuery.Callbacks();
topic = {
publish: callbacks.fire,
subscribe: callbacks.add,
unsubscribe: callbacks.remove
};
if (id) {
topics[id] = topic;
}
}
return topic;
};
})
In order to subscribe to an event the following is done:
$.Topic("message").subscribe(function () {
console.log("a publish has occurred");
});
In order to publish a message the following is done:
$.Topic( "message" ).publish(data);
"Message" is the event name. The data argument contains any information you want passed to the subscribers.
In order to unsubscribe you must pass the function that was subscribed:
$.Topic( "message" ).unsubscribe(funcSubscribedToBefore);
In modern browsers (If I've read the source for Underscore.js right) allow you to bind events to non DOM objects natively. Otherwise, you'll have to use something like underscore's .bind function. So it depends upon what browsers you need to support.
Edit:
Ok, nevermind, I was thinking bind in Underscore.js is the same as with Backbone. Backbone has it's own events module that does event binding, apparently.
binding events to dynamic objects in underscore/backbone
I recently used Ben Alman approach, and it worked great!
/* jQuery Tiny Pub/Sub - v0.7 - 10/27/2011
* http://benalman.com/
* Copyright (c) 2011 "Cowboy" Ben Alman; Licensed MIT, GPL */
(function ($) {
var o = $({});
$.subscribe = function () {
o.on.apply(o, arguments);
};
$.unsubscribe = function () {
o.off.apply(o, arguments);
};
$.publish = function () {
o.trigger.apply(o, arguments);
};
}(jQuery));
Usage:
$.subscribe('eventName', function (event) {
console.log(event.value);
});
$.publish({ type: 'eventName', value: 'hello world' });
See https://gist.github.com/addyosmani/1321768 for more information.
Related
I'll try to explain this weird situation as simple as I can.
I've created an operation hook "before save" and make it in a mixin to add it to some models.
this mixin uses context.options to get current userId to do something.
this mixin is working perfectly if I call the operation directly (like POST /Accounts for example).
But if I call it inside a remote method, the context.options is empty, for example, if we have a method called POST /Accounts/Signup, and inside it, we call Account.create(...), the "before save" hook receives the options as empty object {}
A sandbox project has been hosted here
https://github.com/mustafamagdy/loopback-sandbox-issue
the mixin code snippet is as follows:
module.exports = function(Model, options) {
Model.observe("before save", async function(ctx) {
if (ctx.instance.id) return;
const userId = ctx.options && ctx.options.accessToken && ctx.options.accessToken.userId;
if (userId) {
//... do stuff
}
else
{
console.error("Failed to scope " + Model.name + " to user (null)");
}
});
};
After the investigation, I found this issue that talks about similar behaviour, however, the comments are very destractive. So I thoughlt to write the conclusion here for anyone who are facing the same issue.
Loopback require you to pass the options you declared from the remote method to the model method(s) if you want to receive it on operation hook, so I ended up doing so.
module.exports = function(Note) {
Note.makeNew = makeNew;
async function makeNew(options) {
await Note.create(obj, options);
}
};
I've been using reactive methods to help return my data from some asynchronous meteor methods. This does not seem to work with forms and I was wondering what the work around it? I receive:
Don't use ReactiveMethod.call outside of a Tracker computation.
with the following files:
submit.js
Template.makeTransaction.events({
'submit form': function(event){
event.preventDefault();
// construct the contact object that will be passed to the method
var add = event.target.receiver.value;
var amount = Number(event.target.amount.value);
var comm = event.target.comment.value
var request = {
address: add,
qty: amount,
comment: comm,
asset:'pounds'
};
return ReactiveMethod.call('sendAsset', request, function(err, result){
});
}
});
meteormethods.js
Meteor.methods({
sendAsset: function(request){
var sync=Meteor.wrapAsync(user.sendAssetToAddress, user);
var data = sync({request});
return data;
},
Thanks!
Event handlers (your 'submit form': function(event) {...}) are not reactive. Template helpers are, but they are not the same thing.
What you are doing is a bit strange, since the event handler runs only once, when the event triggers. So in that handler, you should use the "normal" async method of receiving the result of your Meteor.call:
Meteor.call( 'sendAsset', request, function(err, result) {
if( err ) { /* Handle error */ return; }
// Here you use the result.
});
Returning a value from an event handler, as you are doing now, is a bit pointless. There is nothing receiving this value.
I want to be able to fetch data from an external Api for a specific request, but when that data is returned, also make it available in the cache, to represent the current state of the application.
This solution seems to work:
var Rx = require('rx');
var cached_todos = new Rx.ReplaySubject(1);
var api = {
refresh_and_get_todos: function() {
var fetch_todos = Rx.Observable.fromCallback($.get('example.com/todos'));
return fetch_todos()
.tap(todos => cached_todos.onNext(todos));
},
current_todos: function() {
return cached_todos;
}
};
But - apparently Subjects are bad practice in Rx, since they don't really follow functional reactive programming.
What is the right way to do this in a functional reactive programming way?
It is recommended not to use Subjects because there is a tendency to abuse them to inject side-effects as you have done. They are perfectly valid to use as ways of pushing values into a stream, however their scope should be tightly constrained to avoid bleeding state into other areas of code.
Here is the first refactoring, notice that you can create the source beforehand and then your api code is just wrapping it up in a neat little bow:
var api = (function() {
var fetch_todos = Rx.Observable.fromCallback($.get('example.com/todos'))
source = new Rx.Subject(),
cached_todos = source
.flatMapLatest(function() {
return fetch_todos();
})
.replay(null, 1)
.refCount();
return {
refresh: function() {
source.onNext(null);
},
current_todos: function() {
return cached_todos;
}
};
})();
The above is alright, it maintains your current interface and side-effects and state have been contained, but we can do better than that. We can create either an extension method or a static method that accepts an Observable. We can then simplify even further to something along the lines of:
//Executes the function and caches the last result every time source emits
Rx.Observable.withCache = function(fn, count) {
return this.flatMapLatest(function() {
return fn();
})
.replay(null, count || 1)
.refCount();
};
//Later we would use it like so:
var todos = Rx.Observable.fromEvent(/*Button click or whatever*/))
.withCache(
Rx.Observable.fromCallback($.get('example.com/todos')),
1 /*Cache size*/);
todos.subscribe(/*Update state*/);
When user refresh a certain page, I want to set some initial values from the mongoDB database.
I tried using the onRendered method, which in the documentation states will run when the template that it is run on is inserted into the DOM. However, the database is not available at that instance?
When I try to access the database from the function:
Template.scienceMC.onRendered(function() {
var currentRad = radiationCollection.find().fetch()[0].rad;
}
I get the following error messages:
Exception from Tracker afterFlush function:
TypeError: Cannot read property 'rad' of undefined
However, when I run the line radiationCollection.find().fetch()[0].rad; in the console I can access the value?
How can I make sure that the copy of the mongoDB is available?
The best way for me was to use the waitOn function in the router. Thanks to #David Weldon for the tip.
Router.route('/templateName', {
waitOn: function () {
return Meteor.subscribe('collectionName');
},
action: function () {
// render all templates and regions for this route
this.render();
}
});
You need to setup a proper publication (it seems you did) and subscribe in the route parameters. If you want to make sure that you effectively have your data in the onRendered function, you need to add an extra step.
Here is an example of how to make it in your route definition:
this.templateController = RouteController.extend({
template: "YourTemplate",
action: function() {
if(this.isReady()) { this.render(); } else { this.render("yourTemplate"); this.render("loading");}
/*ACTION_FUNCTION*/
},
isReady: function() {
var subs = [
Meteor.subscribe("yoursubscription1"),
Meteor.subscribe("yoursubscription2")
];
var ready = true;
_.each(subs, function(sub) {
if(!sub.ready())
ready = false;
});
return ready;
},
data: function() {
return {
params: this.params || {}, //if you have params
yourData: radiationCollection.find()
};
}
});
In this example you get,in the onRendered function, your data both using this.data.yourData or radiationCollection.find()
EDIT: as #David Weldon stated in comment, you could also use an easier alternative: waitOn
I can't see your collection, so I can't guarantee that rad is a key in your collection, that said I believe your problem is that you collection isn't available yet. As #David Weldon says, you need to guard or wait on your subscription to be available (remember it has to load).
What I do in ironrouter is this:
data:function(){
var currentRad = radiationCollection.find().fetch()[0].rad;
if (typeof currentRad != 'undefined') {
// if typeof currentRad is not undefined
return currentRad;
}
}
I am building a small app primarily with socket io, however with a few things from expressjs.
One function of the socket io piece is to send an email when a certain event occurs. I've got this working fine with node_mailer.
The problem I'm running into is that I want to use the express view engine to render the emails from template files. The render method seems to be explicitly attached to the res object prototype.
What I've done feels pretty dirty:
// setup express server
var render;
app.get('/', function (req, res) {
if (typeof render == 'undefined') render = res.render;
res.end('Welcome to app');
});
// socket io code
socket.on('event', function (data) {
var email_content;
render('template', {}, function (err, result) { email_content = result; });
});
Is there a better way to gain access to expressjs's components outside the context of an http request, or even a better way to approach this problem? I tried rigging up a call to the exported express.view.compile function but that both didn't work and seemed like a high hoo
Here is where the information you seek comes from:
https://github.com/Ravelsoft/node-jinjs/wiki
With templates as modules
To have node load your templates as if they were modules, you first have to register your module extension :
require("jinjs").registerExtension(".tpl");
If you want your file to be transformed prior to being submitted to jinjs, you can pass a callback ;
var pwilang = require("pwilang");
require("jinjs").registerExtension(".pwx", function (txt) {
return pwilang.parse(txt);
});
You can now write this to user Jin:
var my_template = require("./mytemplate");
var context = { foo: "foo", bar: "bar" };
var result = my_template.render(context);
Because you are sticking Jin into express (as opposed to making express work with Jin) this is your best option. The res variable is only available in the route callback.
On express 3.x there is the alias app.render
// socket io code
socket.on('event', function (data) {
var email_content;
app.render('template', {}, function (err, result) { email_content = result; });
});