I have adapted Heroku's direct to S3 upload solution in Rails (which uses jQuery-File-Upload and the aws-sdk gem) so uploads to S3 can be made remotely using ajax. I hope this is useful:
posts_controller.rb
before_action :set_s3_direct_post, only: [:index, :create]
before_action :delete_picture_from_s3, only: [:destroy]
class PostsController < ApplicationController
def index
.
.
end
def create
@post = @user.posts.build(post_params)
if @post.save
format.html
format.js
end
end
def destroy
Post.find(params[:id]).destroy
end
private
def set_s3_direct_post
return S3_BUCKET.presigned_post(key: "uploads/#{SecureRandom.uuid}/${filename}", success_action_status: '201', acl: 'public-read')
end
def delete_picture_from_s3
key = params[:picture_url].split('amazonaws.com/')[1]
S3_BUCKET.object(key).delete
return true
rescue => e
# If anyone knows a good way to deal with a defunct file sitting in the bucket, please speak up.
return true
end
def post_params
params.require(:post).permit(:content, :picture_url)
end
end
posts.html.erb
<div class="info" data-url="<%= @s3_direct_post.url %>"
data-formdata="<%= (@s3_direct_post.fields.to_json) %>"
data-host="<%= URI.parse(@s3_direct_post.url).host %>">
</div>
The form
<%= form_for(:post, url: :posts, method: :post,
html: { class: "post_form", id: "post_form-#{post.id}" }
) do |f| %>
<%= f.text_area :content, id: "postfield-#{post.id}", class: "postText" %>
<%= f.button( :submit, name: "Post", title: "Post" ) do %>
<span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
<% end %>
<span class="postuploadbutton" id="postUp-<%= post.id %>" title="Add file" >
<span class="glyphicon glyphicon-upload" aria-hidden="true"></span>
</span>
<span title="Cancel file" class="noticecancelupload" id="postCancel-<%= post.id %>" >
<span class="glyphicon glyphicon-remove-circle" aria-hidden="true"></span>
</span>
<%= f.file_field :picture_url, accept: 'image/jpeg,image/gif,image/png',
class: "notice_file_field", id: "postFile-#{post.id}" %>
<% end %>
_post.html.erb
<%= button_to post_path(
params: {
id: post.id,
picture_url: post.picture_url
}
),
class: 'btn btn-default btn-xs blurme',
data: { confirm: "Delete post: are you sure?" },
method: :delete do %>
<span class="glyphicon glyphicon-remove" aria-hidden="true"></span>
<% end %>
Javascript in each _post.html.erb
$(document).off('click',"#postUp-<%= post.id %>");
$(document).on('click', '#postUp-<%= post.id %>', function(e) {
prepareUpload("#post_form-<%= post.id %>");
$('#postFile-<%= post.id %>').trigger("click");
});
$(document).off('click',"#postCancel-<%= post.id %>");
$(document).on('click', '#postCancel-<%= post.id %>', function(e) {
$(".appendedInput").remove(); // $('#postFile-<% post.id %>').val(""); doesn't work for me
$('.progBar').css('background','white').text("");
});
$(document).off('submit',"#post_form-<%= post.id %>"); // without this the form submitted multiple times in production
$(document).on('submit', '#post_form-<%= post.id %>', function(e) { // don't use $('#post_form-<%= post.id %>').submit(function() { so it doesn't bind to the #post_form (so it still works after ajax loading)
e.preventDefault(); // prevent normal form submission
if ( validatePostForm('<%= post.id %>') ) {
$.ajax({
type: 'POST',
url: $(this).attr('action'),
data: $(this).serialize(),
dataType: 'script'
});
$('#postCancel-<%= post.id %>').trigger("click");
}
});
function validatePostForm(postid) {
if ( jQuery.isBlank($('#postfield-' + postid).val()) && jQuery.isBlank($('#postFile-' + postid).val()) ) {
alert("Write something fascinating or add a picture.");
return false;
} else {
return true;
}
}
Javascript in application.js
function prepareUpload(feckid) {
$(feckid).find("input:file").each(function(i, elem) {
var fileInput = $(elem);
var progressBar = $("<div class='progBar'></div>");
var barContainer = $("<div class='progress'></div>").append(progressBar);
fileInput.after(barContainer);
var maxFS = 10 * 1024 * 1024;
var info = $(".info");
var urlnumbnuts = info.attr("data-url");
var formdatanumbnuts = jQuery.parseJSON(info.attr("data-formdata"));
var hostnumbnuts = info.attr("data-host");
var form = $(fileInput.parents('form:first'));
fileInput.fileupload({
fileInput: fileInput,
maxFileSize: maxFS,
url: urlnumbnuts,
type: 'POST',
autoUpload: true,
formData: formdatanumbnuts,
paramName: 'file',
dataType: 'XML',
replaceFileInput: false,
add: function (e, data) {
$.each(data.files, function (index, file) {
if (file.size > maxFS) {
alert('Alas, the file exceeds the maximum file size of 10MB.');
form[0].reset();
return false;
} else {
data.submit();
return true;
}
});
},
progressall: function (e, data) {
var progress = parseInt(data.loaded / data.total * 100, 10);
progressBar.css('width', progress + '%')
},
start: function (e) {
progressBar.
css('background', 'orange').
css('display', 'block').
css('width', '0%').
text("Preparing...");
},
done: function(e, data) {
var key = $(data.jqXHR.responseXML).find("Key").text();
var url = '//' + hostnumbnuts + '/' + key;
var input = $('<input />', { type:'hidden', class:'appendedInput',
name: fileInput.attr('name'), value: url });
form.append(input);
progressBar.
css('background', 'green').
text("Ready");
},
fail: function(e, data) {
progressBar.
css("background", "red").
css("color", "black").
text("Failed");
}
});
});
} // function prepareUpload()
create.js.erb
$(".info").attr("data-formdata", '<%=raw @s3_direct_post.fields.to_json %>'); // don't use .data() to set attributes
$(".info").attr("data-url", "<%= @s3_direct_post.url %>");
$(".info").attr("data-host", "<%= URI.parse(@s3_direct_post.url).host %>");
$('.post_form')[0].reset();
$('.postText').val('');
application.js
//= require jquery-fileupload/basic
config/initializers/aws.rb
Aws.config.update({
region: 'us-east-1',
credentials: Aws::Credentials.new(ENV['AWS_ACCESS_KEY_ID'], ENV['AWS_SECRET_ACCESS_KEY']),
})
S3_BUCKET = Aws::S3::Resource.new.bucket(ENV['S3_BUCKET'])
Notes:
This solution is designed for multiple post forms on the index.html.erb page. This is why the @s3_direct_post information is placed inside a div of class info inside index.html.erb, rather than in each post form. This means there is only one @s3_direct_post presented on the page at any one time, irrespective of the number of forms on the page. The data inside the @s3_direct_post is only grabbed (with a call to prepareUpload()) upon clicking the file upload button. Upon submission a fresh @s3_direct_post is generated in the posts controller, and the information inside .info is updated by create.js.erb. Storing the @s3_direct_post data inside the form means many different instances of @s3_direct_post can exist at once, leading to errors with the file name generation.
You need to :set_s3_direct_post in both the posts controller index action (ready for the first upload) and the create action (ready for the second and subsequent uploads).
Normal form submission is prevented by e.preventDefault(); so it can be done 'manually' with $.ajax({. Why not just use remote: true in the form? Because in Rails, file upload is done with an HTML request and page refresh even when you try to do it remotely.
Use info.attr() rather than info.data() to set and retrieve the @s3_direct_post attributes because info.data doesn't get updated
(for example see this question). This means you also have to manually parse the attribute into an object using jQuery.parseJSON() (which .data() actually does automatically).
Don't use //= require jquery-fileupload in application.js. This bug was a real ballache to identify (see here). The original Heroku solution didn't work until I changed this.
