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Rails: Using Ajax to fill Jquery Autocomplete

I've been all over the place plugging different things into this process and I still get no results.
Sometimes I get the infamous extra "<" error, sometimes absolutely nothing happens, and I'm not sure if this is the problem but I think Google developer is showing that the current page is being sent as the json file I'm asking for and not the json I'm sending (see later). This is what I see in google developer:
Which is definitly NOT my json file:
In any case, this is my javascript:
$('#q_name_cont').autocomplete({
url: "autocomplete/items",
dataType: 'json'
});
This is my route:
get 'autocomplete/items' => 'home#autocomplete_items', :defaults=>{:format=>'json'}
Controller Action (commented out part is another method I was trying for a while):
def autocomplete_items
# respond_to do |format|
# format.js {render 'autocomplete_items'}
#products = Item.all.order(:name)
respond_to do |format|
format.html
format.json {
render json: #products.map {|item| item.name}
}
end
end
Before I was using mapping, I was using this view for the render:
{
"items": [
<%Item.all.each do |i|%>
{ "<%=i.name%>","<%=i.name%>" },
<%#end%>
{ "value": "", "data": "" }
]
}
I've really been all over the place, trying for a very long time to get this to work. What am I missing?

IIRC, Your url and dataType options just do not exist in autocomplete's documentation. You could try source option instead:
$('#q_name_cont').autocomplete({
source: function (request, response) {
$.ajax({
url: "/autocomplete/items", // should be with '/'
dataType: 'json',
data: { query: request.term },
success: function(data) {
// call response to return the result to autocomplete box
response(data);
}
});
}
});
Of course, this is just for showing up all items, if you want to filter like real autocomplete box, you should modify controller to filter the result base on query:
def autocomplete_items
#products = Item.all.order(:name)
respond_to do |format|
format.html
format.json {
render json: #products
.where('name ILIKE ?', "%#{params[:query]}%")
.pluck(:name)
}
end
end

Dealing with ajax request in Rails

Stackoverflow community
I have a select in my view. Onchange of which my ajax request is sent.
<%= f.select :id, options_from_collection_for_select(#rtypes, "id", "typeName"),
{include_blank: true },
{'data-rtypes': #rtypes.to_json } %>
.I am using Jquery ajax. My ajax works. It send an id of rtype to the show_sub_types method.
$(function () {
// specify id or class for your select tag
$('select').on('change', function () {
var rtype = $(this).val();
$.ajax({
url: "/RequestTypes/show_sub_types/"+rtype,
type: "GET",
})
});
});
In my show_sub_types method I want to grab all subTypes (stypes) from RequestSubType model.
def show_sub_types
#rtype = params[:id];
#stypes = RequestSubType.where("RequestType_id"==#rtype).all
respond_to do |format|
... some code here
end
end
I do not know how to deal with ajax request, i dont know how to send my stypes array to the page, and how to deal with that response. I have read some tutorials, but still can not understand that respond_to part. Probably i would understand on my own example.
In my view i have div where i want to put data send by ajax (inserted into html).

Specify the id of select and read for data attribute.
Get that array in data variable, and pass it to post ajax request
var data = $(this).data('rtypes');
or
$(this).find(':selected').data('rtypes')
$.ajax({
type : "POST",
url : "/RequestTypes/show_sub_types/"+rtype,
dataType: 'json',
data: JSON.stringify(data),
dataType: "json",
contentType: 'application/json'
});

What am I doing wrong with this AJAX request using a form_for in Rails 4?

I'm trying to do a form submission through AJAX in Rails and I am not too sure what is wrong here. I got everything to work using "remote: true" but I want to gain a better understanding of how the AJAX works with jQuery. This is my javascript code:
$(document).ready(function(){
$("#new_user_friendship").on("submit", function(event){
event.preventDefault();
var friendId = $("#user_friendship_friend_id").val();
var _this = $(this);
$.ajax({
url: "/user_friendships",
data: _this.serialize(),
method: "POST",
dataType: "json",
success: function(data){
console.log(data);
friendButton.hide();
$(".friend-request-form").html("<p>Friend request sent</p>");
}
});
});
});
I am suspecting this line url: "/user_friendships/new?friend_id="+friendId containing the url is the culprit of my errors. I wrote this because a hidden field is being passed as a person's friend id but it throws a "404 error", I've also tried url: "/user_friendships" which doesn't return any errors but it also doesn't properly execute the Javascript as I expected.
This is the corresponding form_for that the AJAX request is sent to:
<div class="friend-request-form">
<%= form_for current_user.user_friendships.build(friend_id: #user), id: "new_user_friendship", method: :post do |f| %>
<%= f.hidden_field :friend_id, value: #user.id %>
<%= submit_tag "Send friend request", class: "button radius tiny", id: "friend-request-button" %>
<% end %>
</div>
What this form does is it sends a friend request to another user using a hidden field.
And in my user_friendships_controller.rb I have this code:
def create
if params[:user_friendship] && params[:user_friendship].has_key?(:friend_id)
#friend = User.find(params[:user_friendship][:friend_id])
#user_friendship = UserFriendship.request(current_user, #friend)
respond_to do |format|
if #user_friendship.new_record?
format.html do
flash[:error] = "There was a problem creating that friend request."
redirect_to user_path(#friend)
end
format.json {render json: #user_friendship.to_json, status: :precondition_failed}
else
format.html do
flash[:success] = "Friend request sent"
redirect_to user_path(#friend)
end
format.json {render json: #user_friendship.to_json, status: :precondition_failed}
end
end
else
flash[:error] = "Friend required"
redirect_to root_path
end
end
If anyone can provide any suggestions or feedback that'd be great!
UPDATE:
Now that I added in data: _this.serialize() and changed the url to: url: "/user_friendships" I'm now getting a 412 (Precondition Failed) error. Despite this error the data is actually being saved into the database. Does anyone know why I'm getting this 412 (Precondition Failed) error?

There is something I do not understand, with the dataType json, you said that you had a precondition failed status right ?
But you wrote
format.json {render json: #user_friendship.to_json, status: :precondition_failed}
So I don't think there is any problem, indeed, it seems to work fine, as you explicitly passed the status in your render command, try removing it and I think you will have a 200 (success) status instead.
Of course, you can keep the previous post ajax request, or use this short version
$.post(
/user_friendships',
{ user_friendship: { friend_id: friendId } },
function(){
console.log(data);
friendButton.hide();
$(".friend-request-form").html("<p>Friend request sent</p>");
},
'json')

Add a data attribute to the post params instead of passing it in the url:
$.ajax({
url: "/user_friendships",
data: { user_friendship: { friend_id: friendId } }, // <<< Updated
method: "POST",
dataType: "json",
success: function(data){
console.log(data);
friendButton.hide();
$(".friend-request-form").html("<p>Friend request sent</p>");
}
});
Update
The url should be /user_friendships, assuming that you're using RESTful actions. Have a look to this article about REST in Rails.
Also, when you do an AJAX request like this, your are not sending the rails authenticity tokens that are crated by the form helper. This may be the cause of your 412 (Precondition Failed) error.
See: Understanding the Rails Authenticity Token

Json sending multiple results

I send data in json format for counting visits. Problem is when i use back arrow in browser - results are send second, third ... and more times and there is one em tag for every click in back arrow on browser. What i can do to overwrite results but not sending second in new place.
My controller:
visits_count = current_user.visits.where(:read => false).count.to_i
respond_to do |format|
format.json { render :json => visits_count }
And my js:
function unread(){
$('#visits p').each( function() {
$.ajax({
url: '/visits/unread_count',
dataType: 'json',
success: function(data) {
if (data > 0) {
$('#visits p').append('<em>' + data +'</em>');
}
}
});
});
};
and my view:
<%= link_to 'visits', visits_path, :id => "visits" %><p></p></li>

Reload controller variables in view

In a rails application i am working on, i would like to refresh/reload the index method of my controller without refreshing the view. For instance lets say i have this as my index:
def index
#title =params[:title]
end
And html.erb:
<script>
function changeField() {
var newTitle = "Alerts"
$.ajax({
url: 'index?title=' + newTitle,
type: 'POST',
contentType: 'application/json',
data: '',
dataType: 'script',
headers: {
'X-CSRF-Token': '<%= form_authenticity_token.to_s %>'
},
complete: function () {
alert('<%=#title%>');
}
});
}
</script>
<button type="button" onclick="changeField()"></button>
The problem i am having is that it does not reload the #title variable on the view so i get the original title and not the new title.

When page was loading alert('<%=#title%>') equals alert('first value') and after set a new value javascript code can't be reloaded. If you look html code you can see first value but not second
I think you can add this code to you controller
respond_to do |format|
format.html # index.html.erb
format.js { render :json { :title => params['title'] || #title }.to_json }
end
and add to js code success: function(data) { alert(data['title']) }