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Rails 5.2. Rendering a js.erb partial from a helper method

I have a model called Question, and it has action create;
My goal is to display a flash message instantly, using a helper method (show_alert for example) when the instance is not valid.
question_controller.rb
def create
question = Question.new(question_params)
if question.save then
redirect_to show_question_path(question.id)
else
show_alert(:warning, question.errors)
end
end
application_controller.rb
helper_method :show_alert
def show_alert(type, message)
#type = type; #msg = message
respond_to do |format|
format.js { render :template => 'alert.js.erb'}
end
end
alert.js.erb
var div = $('<div></div>').addClass(`alert alert-${#type}`)
$('<ul></ul>').append( $('<li></li>').html(#msg)
div.append(ul)
$('#alerts').html(div)
But instead of displaying the flash, I get only the partial's code on the white screen.
see the screenshot
Since I've used respond_to I got another error: ActionController::UnknownFormat
I need the snippet of code in alert.js.erb to be executed, in order to render the flash, I think the trick is somewhere in the render function, but two hours of googling were just a waste of time.
Please help! Thank you in advance

ActionController::UnknownFormat error is showing up because the browser is sending HTML request to Rails server, but the respond_to block has only specified what to do in case of a javascript request from web server.
You will need to add a little bit of Ajax to achieve what you want. See this tutorial on Ajax. https://www.tutorialspoint.com/ruby-on-rails/rails-and-ajax.htm
Ajax will send a js request to browser in the background (i.e the browser will not refresh or show any signs of loading). This js request will be sent to Rails server and it will return the .js.erb file containing the script back to the browser. Now since this script was returned as a response to Ajax request by browser, the browser will already know that it is javascript that needs to be executed.
If you do not wish to implement Ajax, you have the alternate of doing something like this in your create controller:-
def create
question = Question.new(question_params)
if question.save then
redirect_to show_question_path(question.id)
else
redirect_to new_question_path(error: question.errors) #new_question_path is the action that displays the question form to the user
end
end
and then you can initialize an error variable in the action that displays the question form. e.g.
def new
#error=params[:error]
#rest of the code...
end
And then in somewhere in your new.html.erb (or whatever the html.erb file name is)
<script>
<% if #error %>
var div = $('<div></div>').addClass(`alert alert-<%= #type %>`)
$('<ul></ul>').append( $('<li></li>').html(<%= #msg %>)
div.append(ul)
$('#alerts').html(div)
<% end %>
// you might need to tweak the variable names in controller or the above code
</script>
(This code above may not be perfect. its just to give u an idea)
However this approach will not be as quick and beautiful as ajax because when the user will submit their question, the entire page will load again to display the error warning.

By default, all output from helpers is escaped. To show the HTMl as-is, you need to use the html_safe method (https://apidock.com/rails/v4.2.1/String/html_safe). See Using helpers in a view escapes the html?

I cannot be sure this without seeing your alert.js.erb but it could be that you need to use escape_javascript in your alert.js.erb
Something like (and I haven't tested this out) in your alert.js.erb
$('<%= escape_javascript("#{type} - #{msg}") %>').appendTo("#alert")
You can read more about it on Rails Guides - Working With Javascript in Rails
Hope this helps!

Problems submitting AJAX request in Rails 4

I've been following http://blog.markhorgan.com/?p=522 as a guide to update an image in a form with an ajax callback. Image saves fine but I want to do some clever ajax so the page doesn't refresh.
Here's my code:
edit.html.haml:
#promo-image
= render partial: 'promo_image'
_promo_image.html.haml:
= form_for( #property, remote: true) do |f|
= f.file_field :promo_image, :pattern => "^.+?\.(jpg|JPG|jpeg|JPEG|png|PNG|gif|GIF)$", :id => 'promo-image-upload'
= f.submit 'Update'
= image_tag #property.promo_image.url(:medium)
properties_controller.rb
def update
#property = Property.find(params[:id])
if #property.update(property_params)
format.js
else
render 'edit'
end
end
update.js.haml:
$("#promo-image").html("#{escape_javascript(render partial: 'promo_image',)}");
With the code outlined above I get error pointing to the format.js line:
ArgumentError in PropertiesController#update too few arguments
Can anyone see where I'm going wrong or perhaps point me in the right direction?
Many thanks!
Steve
UPDATE
Just to be clear, I want to be able to update JUST the Div stated here:
update.js.haml:
$("#promo-image").html("#{escape_javascript(render partial: 'promo_image',)}");
This code works, but refreshes the whole page:
respond_to do |format|
format.html { redirect_to edit_property_path(#property) }
format.js
end
FURTHER UPDATE
Just to be clear on my motives, I want to be able to update an element on the edit page, and not be redirected to a different one, e.g. show or index. This is for UI reasons. The guide above talks about the exact same thing.
FINAL UPDATE
The issue is because I'm using a file upload, this can't be achieved via ajax. For those in a similar situation see here: Rails form_for with file_field and remote => true and format => :js
A solution could lay here, and I will investigate this: https://github.com/JangoSteve/remotipart
Thanks to everyone for helping me work out the error of my ways!

Regarding your first update, you said that this code works, but refreshes the page:
respond_to do |format|
format.html { redirect_to edit_property_path(#property) }
format.js
end
If that is the case, that means the incoming request is an html request, rather than an AJAX request. So the format.html block runs and redirects the browser to the same page, which now has the updated image.
What you need to do is figure out why the page is not sending the request as AJAX. You can see the request format if you look at the terminal output (if running locally). It will say something like:
Processing by ControllerName#action as [format]
Format needs to be JS in order for the format.js to render update.js.haml.
UPDATE:
Now that you mention it, the issue is indeed the file_upload field. Uploading files with AJAX is actually not possible with the Forms Helper. See the docs:
Unlike other forms making an asynchronous file upload form is not as simple as providing form_for with remote: true. With an Ajax form the serialization is done by JavaScript running inside the browser and since JavaScript cannot read files from your hard drive the file cannot be uploaded. The most common workaround is to use an invisible iframe that serves as the target for the form submission.
I did a quick search on Google and found the remotipart gem, which seems to specialize in doing this. I don't have any experience with it though, so you're on your own from here on. :)

Try changing your update action to
def update
#property = Property.find(params[:id])
if #property.update(property_params)
respond_to do |format|
format.html { redirect_to properties_path }
format.js
end
else
render 'edit'
end
end
Source

Rails 3, rendering partial view through ajax

I'm making an e-mail service with mailboxer gem.
In my index view I have several links that will lead to inbox/draft... like this:
<%= link_to "Inbox", show_conversations_path, :remote => true %>
...
<div id="content">
</div>
Then my show_conversation js.erb
$("#content").html("<%=escape_javascript(render :partial=>"show_conversations")%>");
the controller (messages_controller)
def show_conversations
#inbox = current_user.mailbox.inbox
respond_to do |format|
format.js
end
end
And there's also a partial view _show_conversations.html.erb (already tested, through a simple render so no errors there).
So my problem is that, when I click on the link, it actually redirects to a blank plage (when it shouldnt, or at least it's not my intention, redirect at all, just show the content on the div).
I've realized that it actually renders its controller, then the erb.js, the partial view, and I Don't know why the controller again but this time as HTML.
A piece of the log:
Started GET "/en/messages/show_conversations"4
Processing by MessagesController#show_conversations as JS
...
Rendered messages/_show_conversations.html.erb (7962.4ms)
Rendered messages/show_conversations.js.erb (23239.0ms)
Completed 200 OK in 23330ms (Views: 23237.9ms | ActiveRecord: 5.0ms)
Started GET "/en/messages/show_conversations
Processing by MessagesController#show_conversations as HTML
Completed 406 Not Acceptable in 8ms (ActiveRecord: 0.5ms)
I know it shouldn't redirect, and I believe it shouldn't call two times to the controller (and the second one as if it was html instead of js), but I don't really know why it's happening nor have I found a similar problem through the forum

Check with below code, if it works
def show_conversations
#inbox = current_user.mailbox.inbox
respond_to do |format|
format.js { render :layout => false }
end
end

Try modifying this line:
$("#content").html("<%=escape_javascript(render :partial=>"show_conversations")%>");
to:
$("#content").html("<%= escape_javascript(render :partial=>'show_conversations') %>");
or make it pretty:
$("#content").html("<%= j render :partial=>'show_conversations' %>");

Simulating Rails form submit in JavaScript

I have a pretty standard Rails HAML new object form that does the usual stuff and ends with:
= f.submit "Add scenario"
This works perfectly, and the scenarios_controller.rb is also a straightforward:
def create
...create scenario...
redirect_to scenarios_path
end
However, I have also developed a wizard-type form that needs to do some JavaScript on pressing my button:
= f.submit "Add scenario", :onclick => "return validateForm()"
In my CoffeeScript, I collect up all the information and finish up with:
$.post(
url
data
(data, textStatus, jqXHR) ->
# How do I follow the redirect?
return false
My url and data are correct as the above controller works correctly and creates my object, but my page doesn't redirect to scenarios_path. I think I should be doing something with the post result, but searching around the web I cannot find out what, and examining the returned fields in Chrome's debugger doesn't suggest anything. The only suggestion I saw was to use data.redirect, but such a field doesn't exist, although jqXHR.responseText seems to contain the page I want to redirect to.

I'd treat the HTML call to Scenario#create and the JS call to Scenario#create differently, using a respond_to block.
In your scenarios_controller.rb file:
def create
# create your object
respond_to do |format|
format.html do
redirect_to scenarios_path
end
format.js
end
end
In views/layouts/scenarios/create.js.erb, then put something like:
window.location.replace("<%= scenarios_path %>");
When you call Scenario#create with JS, the create.js.erb file gets rendered and forces the redirect. When you call Scenario#create with HTML, the redirect_to call happens as usual.

Rails update.js.erb not executing javascript

I am building a form in rails that will edit an existing question via ajax.
After the form is submitted and the question has been updated, the update method in the controller renders update.js.erb, which will hide the form again.
My problem is that the javascript code in update.js.erb is not executing at all.
I know that the file is rendering because it shows up in the server output, and when I put a
<% raise params %>
into it, it works.
However, even the simplest
alert('hello');
has no effect in the same file.
I've ruled out javascript and jquery configuration issues because the same code works perfectly in my edit.js.erb file. It's just not working in update.js.erb.
What am I missing?
Edit:
Firebug shows no errors. Here is the response in firebug's network panel:
alert('hello');
$('#question_body').replaceWith('<h4><p>jhsdfjhdsb k jdfs j fjfhds <strong>jfshaflksd;hf sdldfs l fdsalkhdfskhdfs</strong>;fd lfdksh hfdjaadfhsjladfhsjadfs ;df sjldfsj dfas hafdsj fdas ;ldfas ldfs df dl;hdf fdh ;fdj ;lfads</p></h4>');
def update
Edit 2:
This is the controller action:
def update
respond_to do |format|
if #question.update_attributes(params[:question])
format.html { redirect_to #question, :flash => { :success => 'Question was successfully updated.' } }
format.json { head :no_content }
format.js {}
else
format.html { render action: "edit" }
format.json { render json: #question.errors, status: :unprocessable_entity }
end
end
end

In your $.ajax call make sure to set the dataType option to "script" otherwise the response could be interpreted in other ways and thus not executed as JS.

Do you work with haml, or html.erb? If the former, then this might be the solution:
respond_to do |format|
...
format.js {render layout: false}
end
I had the exact same problem, found this question early on, took another hour or so of Googling to find this question on StackOverflow that led me to it: jQuery + Ajax + Haml. js.erb files not firing

In your update.js.erb file you need to escape javascript wherever you execute ruby code.
$('.container').empty().append('<%=
escape_javascript(
render 'update'
)
%>')
This is what solved it for me ...

This issue isn't just because of Controller side. It is also can be in the View side which is you didn't clarify the data-type of your post request.
Make sure in your console that the request is treated as JS.
Reference: Similar issue

I ran into the same issue and found this page. I tried methods listed here but found no luck. While later the following method solve my issue.
My originally code was:
$('#html_id').html('<%=#ruby_variable%>');
And I updated it to:
$('#html_id').html('<%=raw #ruby_variable.to_json%>');
Now it works as expected.

Found out what it is! 😊 (solution for rails 4)
If you have in your ajax call parameters that are not in your permitted list, the record gets saved, you get no error messages about the 'not permitted' parameters, but the update.js.erb won't run - even though your terminal will feed back 'Rendered update.js.erb etc'
If the extra parameter is an attribute in your model, just permit it.
The simplest way to permit non model parameter is to add in your model:
attr_accessor :paramKeyTroublesome
Then you can also permit it in the controller.
in the $ajax call, data needs to be hashed up properly:
data: {model_name: {paramKey1: value, paramKeyTroublesome: value}}

One more problem to be aware of is an error in your update.js file. Nothing will execute if there are any syntax errors. You can check this by going to your browser inspector and enabling Log XMLHttpRequests Then reviewing the output js file.