Develop Reference

Rails update element based on AJAX request?

I've been reading a lot about Rails and AJAX and 5.1 Unobtrusive javascript. It explains a lot about responding to Rails version of AJAX calls with a .js file for example.
However what im wanting to do isn't serving up an entire .js file, it's simply updating an element after a <% link_to %> POST request. From my understanding setting remote: true submits it as a AJAX request.
Essentially I have a "Post" which a user can like via a linked Like button. This sends a POST request to the "Post" controller which updates a post to liked and adds a like to the post.
Unfortunately to see the effects of the post being liked (Which is simply that the link changes color as well as the font-awesome icon) you need to refresh the page. I basically want it to update without needing refresh.
I "think" based off what i've read I need to make a respond do and respond via .js to the request with a .js file in the view I want to update (for instance if the controller action is called "like", maybe a like.js.erb file in the view im updating?). But I don't want to serve an entire new page..or would this simply just run the .js?
Then I could do something like $('i.fa-icon#id').style.color = "blue" or something? (Im assuming I can send data from the controller to the .js.erb file?). Not sure the best way to do this, don't rails elements a lot of times have some sort of data-attribute or something (Im still a beginner at this).

Your description is quite correct!
Opposed to the other answer, you don't even need a event listener but as you said you want to have a respond_to in the controller.
So starting from the html:
# post/index.html.erb
<div id="like-button">
<%= button_to "Like this post", post_path(#post), remote: true %>
</div>
Note, that when you use a button_to helper it'll be a POST request by default.
If you click it, it'll go to the controller#update, which you want to change to this:
#posts_controller.rb
...
def update
#post.save
respond_to do |format|
format.html { redirect_to post_path(#post) }
format.js # <-- will render `app/views/posts/update.js.erb`
end
end
Note: the format.html is rendered when JS is disabled.
Now in the scenario that JS is enabled, it executes the app/views/posts/update.js.erb file. It can look like this:
const likeButton = document.getElementById('like-button');
likeButton.innerHTML = '<%= j render "posts/liked-link", post: #post %>';
What is the last line doing? Of course, you can change the style directly with the JavaScript, but you can also render a new partial - and this you will create in a new html file:
# app/views/posts/liked_link.html.erb
<div id="like-button ">
<p>"You liked this post!" </p>
</div>
I just changed the link/button to ap now, but of course you can do whatever you want.
Hope that makes sense :)

Not sure if I understand the question, but if you want to update like button:
What you want to do is to add an event listener to the button, and when clicked it makes a POST request to whatever route handles the likes(with the correct parameters) and your controller should respond with the like object (or whatever in the database gets stored). Have your post request on success method to grab the like button and change it to whatever you want it to look like
$(“#like-btn”).click(function(){
Rails.ajax({
url: "/some/url/to/like/controller",
type: "post",
data: [your post data],
success: function(data) { $(`#${ data[“btn-name”] }`).attr(“color”, “blue”; }
})
}
You can stick this script right in the bottom of the html page
You don’t have to do it exactly like this, just giving you an idea of how to set up the pattern of having JavaScript and Ajax handle the post request and updating of the frontend instead of using html buttons

When javascript loop inserts HAML partials, does server begin rendering partials before loop finishes?

I'm working on displaying JSON from ajax request with Ruby on Rails but would like to know the following as it would help in the way I layout my code.
Does server immediately render haml/erb partials inserted via javascript loop via javascript escape function(rails) or would javascript loop finish inserting partials and then server would render all partials? Rails 4.2.4
Will see if I can test this to find out in the mean time.

Found it, server renders all inserted partials at one time.
Tested with looping though, setting console logs, inserting partials and setting timeouts.
Partials render all at once but even before console log shows message. Have more questions now but will have to look online for more info.
// Lets Begin
console.log("Now... Lets begin js.erb");
var data = "<%= escape_javascript(#data.to_json.html_safe) %>";
handler = JSON.parse(data);
console.log(handler);
console.log("this was the hanlder");
// Javasscript now has the data!! Lets begin to manipulate it.
$("#button").fadeOut("slow");
// Loop to test output
for (i in [1,2,3,4,5,6]){
setTimeout(function (){
console.log("Here we go");
},5000)
$("#table").fadeIn("slow");
$("#table").append("<%= escape_javascript(render 'table') %>");
setTimeout(2000)
};

Ajax Partial Refresh by Polling in Rails 3, jQuery

Rails 3, JRuby
I recently took part in a quick crash course in jQuery that included a bit of ajax partial rendering. This got me thinking, could I use this to poll the Rails server using setInterval(), every x seconds to refresh a specific part of my page constantly?
The problem I'm having is how I could use the $.get() method to grab the url of the partial and reload it using load(). This is where the confusion starts- using Rails 3, I have a partial called "_microposts", rendered within a div with an 'id="gf" ' (gf meaning global feed). This happens on my Rails app homepage, so the url in this case would be "//localhost:8080/home" and not the url of the partial.
Here is my initial javascript/ jQuery
<script>
$(document).ready(function() {
setInterval(function (e) {
var url = $.get("<%= escape_javascript render :partial =>
'microposts/micropost', :locals => {:microposts => #microposts }%>");
$('#gf').html('loading...').load(url);
},10000);
});
</script>
This looks wrong, and so far, just blanks out my _microposts partial after 10 seconds (so the setInterval is working, and it's definitely updating the correct area, just with a blank space!)
Edit:
Thinking about my problem, I realised that this is similar to updating a partial from an event, such as clicking a button or something. The only real difference is the "event" that should trigger this the setInterval() function. So, my revised jQuery code is as follows:
<script>
$(document).ready(function() {
setInterval(function (e) {
$('#gf').html("<%= escape_javascript render :partial =>
'microposts/micropost', :locals => {:microposts => #microposts } %>")},
10000);
});
</script>
Unfortunately now, nothing seems to be happening from a user point of view, but the server is showing an ajax request every 10 seconds.
So why can't I poll for updates using ajax, and apply the changes to my _microposts partial? Is $.get the correct function to use in this case? What would the url for the load() method be when trying to re-load a partial?
Thanks,

Hopefully this will help anybody who wants to refresh a partial using ajax- especially if you're a beginner following Michael Hartl's tutorials to learn Ruby on Rails. Here's how I managed to solve my problem.
Firstly, I created a separate .js.erb file in the micropost view folder called 'polling.js.erb' that will refresh the global feed partial.
$('#gf').html("<%= escape_javascript render :partial =>
'microposts/micropost', :locals => {:microposts => #mps} %>");
I needed to write a method in the micropost controller that will correspond with the above javascript- this essentially supplies the information needed to refresh the partial. It's basically a simplified version of my index method in the micropost controller and avoids executing the additional code that's not needed for the partial I want to refresh.
def polling
#mps = Micropost.all #add some paginate code if you wish
#micropost = current_user.microposts.build(params[:micropost])
end
I then revised my javascript code, as I wanted to call the polling method every 5 seconds, loading the information specific to the current_user of my webapp.
$(document).ready(function() {
setInterval(function () {
$.ajax('microposts/<%= current_user.id %>/polling');
} , 5000);
});
Finally, I updated my routes.rb file to allow a web browser to call my polling method, using a get request, without causing a routing error. I'm using a member do block because the request is passing the current_user id via the request.
resources :microposts do
member do
post :polling
end
end

Dojo request.post to Rails Fails

I'm converting a website from Symfony to Ruby on Rails and am finally down to my javascript pop up email contact form. I don't want to rewrite the form or the java script as it took a lot of work to get it to work in the first place. That will be phase two.
Here's where I'm having the problem:
sendBtn = new Button({
label: "Send",
onClick: function(){
if (emForm.validate() == true){
// Post the data to the server
request.post("/contact/create",
{data: domForm.toObject("contact-form"),
// Wait 2 seconds for a response
timeout: 2000
}).then(function(response){
emailDialog.hide();
alertDialog.set("content",response)
alertDialog.show();
});
}
}
},"submit-btn");
I know it gets to the request.post as I copied the line "email.Dialog.hide()" just before it and it hid it. I later added code to catch any errors. It goes there immediately and not after the two second timeout. I'm using dojo here, by the way. So I suspect it doesn't like the "/contact/create" as it's the only thing I changed.
In my routes.rb I have:
get 'contact/create'
Do I have the right information in my post? If not how do I get there? The javascript is included in application.html.erb so it can be invoke from all pages on the site.
In case it's pertinent, my contact_controller.rb is currently just this:
class ContactController < ApplicationController
def create
respond_to do |format|
#format.html {}
#format.js {}
format.json { render :json => {:response => 'Amazing, it works'} }
end
end
def show
end
end

Take a look at your network tab in dev tools, it should tell you why it is failing post... I'd say try adding handleAs: 'json' option to your request.post. For more on dojo/request, read this

As it turned out, I had the right path in the request.post statement. I found out my copying the Javascript into my html.erb file so I could use
<%= contact_create_path %>
in it's place. I ended up getting the same value so that wasn't the problem. I then checked my Firebug console. Rails sends a nice dump of the problem. I was getting a 404 error. The problem was that I was doing a post and there was no route for it. So I changed the routes.rb file from
get 'contact/create'
to
post 'contact/create'
This might cause me other problems later on if I want to do a non-Javascript version.
I then got another error:
ActionController::InvalidAuthenticityToken in ContactController#create
Through the help of Stackoverflow I found the fix. I added the second line below:
class ContactController < ApplicationController
skip_before_filter :verify_authenticity_token
...
Again, this solution may cause other problems. Skipping verification doesn't seem like a good thing. I had a number of other problems getting the whole process to work, but their specific to my application.

Include a Coffeescript file with ERB in a view

This is giving me a major headache...
So I have an app which requires a sidebar that lists various information to do with a user's player. One section of this sidebar is a friends list. Now, when Player A sends a friend request to Player B, the request should be automatically logged in B's sidebar, and I intend to use WebSockets to do this.
Here is my cp.js.coffe.erb file (there's only a few snippets of ERB at the moment; there will be loads more and I rather get this working first):
$ ->
$("#cp").accordion()
if `"WebSocket" in window`
socket = new WebSocket("ws://localhost:8080")
socket.onopen = =>
console.log("Connection Open")
init = {
sender: "cp"
action: "init"
user: <%= #user.id %>
token: <%= cookies["remember_token"] %>
}
socket.send(init.to_json)
socket.onerror = (e)=>
console.log(e)
socket.onclose = =>
console.log("Closed")
socket.onmessage = (m)=>
console.log("Recieved: #{m.data}")
msg = m.data.JSON.parse
switch msg.action
when "ret_init"
when "friend_udt"
refreshFriend()
refreshFriend() ->
html = "<%= j render 'layouts/friends' %>"
$('#friends').empty()
$('#friends').add(html)
Theoretically, the code itself works fine, the problem being that Rails doesn't let you use ERB in the assets pipeline, and so this file has to sit in app/views/layouts.the file cannot access the variables declared within a controller or use the render method (or most other ERB methods).
Here's the thing: I can't include said file in my application.html.erb file, and I looked into requesting the file with AJAX, but from my understanding that will immediately execute the Javascript once and once only, and I need the methods in this to be constantly available to update the sidebar.
Is there any way of including this file so that it works with the ERB and the CoffeScript so that it would be continuously avaliable to the page? Am I misunderstanding the whole AJAX requesting method?
Thanks #nzifnab for your help with the JS. Now my friends partial looks like this:
<ul id="friendlist">
<% if Relation.find_by(owner: #user.id, type: "freq") != nil %>
<% Relation.find_by(owner: #user.id, type: "freq").each do |r| %>
<li class="friend-request-cp"><%= link_to "/#{User.find(r.character).name}" %></li>
<% end %>
<% end %>
<% if Relation.find_by(owner: #user.id, type: "friend") != nil %>
<% Relation.find_by(owner: #user.id, type: "friend").each do |r| %>
<li class="friend-cp"><%= link_to "/#{User.find(r.character).name}" %></li>
<% end %>
<% end %>
</ul>
I need to apply two different styles to each item, hence why I'm using the ERB here. This works fine, as it's loaded when the page is first navigated to, but my code was supposed to re-render that partial every time a notification comes through of any new interactions. It would then repopulate the list using the data from the database again. Is there a more efficient way of doing this? Can I still do this with the hamlcoffeeassets gem you showed me?
Slight tangent ensues:
By the way, I'm using Ruby 2.0.0-p247 and Rails 4 on Windows 7. I felt the need to include that because of some major compatibility issues with gems that are much different from Ubuntu. I had to move from Ubuntu to Windows because updating from 13.04 to 13.10 broke everything Ruby Gem on that OS. I don't have tome to find a fix: I literally have only four days to get this app built.

You can kinda use erb in the asset pipeline, but you have to remember that it only gets rendered ONCE, EVER, and not once for every user and so even if there was an #user variable (which there won't be), it would never change. You can use erb in your coffee file for things like route paths and environment variables, but not for things like user-specific config and dynamic changes to the JS. It's bad practice anyway.
What you should really do is use a javascript library to read cookies instead of trying to do it with rails (This will give you access to some of the things you appear to be trying to do). And when you need more dynamic behavior you should render data-attributes or other values into the html DOM itself and use the javascript to read that.
Take a look at this cookie library: https://github.com/carhartl/jquery-cookie
There's many others to look at via a quick google search.
socket.onopen = =>
console.log("Connection Open")
init = {
sender: "cp"
action: "init"
user: $.cookie('user_id')
token: $.cookie('remember_token')
}
There are a couple of ways to render new markup for your view using JS. One way is to use js templates. I'm a big fan of the hamlcoffeeassets library here: https://github.com/netzpirat/haml_coffee_assets Although it uses haml for the view, and not ERB. There are ERB variants as well.
You would add some markup to app/assets/templates/friend.jst.hamlc like so:
%p This is my friend markup #{#friend.name}
And then you can render it from your JS like this:
$('#friends').append(JST['templates/friend'](friend: {name: 'Bob'}))
Which will append the markup from your template with the values you've passed interpolated in. In my example you'd end up with this markup inside your #friends container:
<p>This is my friend markup Bob</p>
Alternatively you can render the partial you want via rails into your JSON response as just a string, and then insert that into your document...
So your JS might look something like this:
socket.onmessage = (m)=>
console.log("Recieved: #{m.data}")
msg = m.data.JSON.parse
switch msg.action
when "ret_init"
when "friend_udt"
refreshFriend(msg.friendHTML)
refreshFriend(html) ->
$('#friends').html(html)
UPDATE
In reference to your ERB question... First of all your partial is incredibly inefficient making similar calls to the database four times every time you render it. haml_coffee_assets is for use with the haml markup language (which I prefer over ERB), if you want ERB then use eco instead: https://github.com/sstephenson/eco
If you want to render this in the JS, then you need to send this "friend relation" data as JSON through the notification data response, you do not have access to active record OR any controller methods or instance variables when rendering javascript partials - they don't hit back to the server, they only use what is accessible by your javascript at the time.

This should really go to app/assets/javascripts/cp.js.coffee.erb, you can use erb in the asset pipeline just fine (see here) Make sure you are spelling the coffee extension right, though!
Doing this, you should be able to call this via ajax without problems, the path would be /assets/cp.js.

try this gem: 'coffeebeans'
name your coffee file as "some_file.html.erb"
<%= coffeescript_tag_do %>
# your coffee script here ...
<% end %>
in another erb file:
<%= render file: '.../some_file' %>