I've managed to make it work, and I have some knowledge about how it works, so I'm going to share this knowledge. But I want to strongly point out, that I have figured this on my own, so there might be flaws in what I'm providing. Use your knowledge and experience, and if you think something can be done better, you may be right.
First of all, download the library using npm. I have found two gems for it, but don't use them. At the time I'm writing this, those gems are outdated, and won't be working. Github links:
github.com/mezis/fineuploader-rails
github.com/zakgrant/fine-uploader-rails
If you happened to download those, you will have to reinstall library.
After that, you will be creating the javascript. I've created a file called "fine-uploader.coffee", and put there something like this:
$ ->
uploader = new (qq.FineUploader)(
element: document.getElementById('fine-uploader')
request:
endpoint: '/upload'
params:
authenticity_token: $('#fine-uploader').data('authenticity-token')
template: 'template-name'
chunking:
enabled: true
mandatory: true
success:
endpoint: "/upload/finish"
)
I'm not going to describe what is what, because all of this can be found in the docs, instead I'll focus on what is important for us.
In the "request" you have an endpoint, for this case, we will need to add it to our routes, like this.
post 'upload', to: 'uploads#create'
Then, we will need to create our controller. As you can see, I've created dedicated controller for handling uploads, and I recommend you doing so.
In the uploads controller we have this action:
def create
file = params[:qqfile]
#code that does whatever you need
respond_to do |format|
format.json {
render json: { success: true }
}
end
end
In your controller, you will have some params (you can check all of them in the docs), but the one that is important to you is qqfile. This will be the file, that was posted. You can do whatever you want with it. I was using carrierwave to save and process it, and I guess this does not require further description (as you can find it in the carrierwave dosc, also, you maybe using something else, like refile).
You will also have to add a parameter with token, you can see it in the 7th line of the javascript file. I recommend reading about CSRF tokens.
Important thing is, that if you chosen (like me) the chunking option, this will NOT be the whole file, only the part of it. You can find bigger tutorials on how to handle parted files, but what you need to pay attention for is the qquuid that you will be send in params. This id identifies the file that is being uploaded, and you will need it to determine to what file uploaded part belongs, so you don't mix two files up. Every part is being send by separate post request, so I recommend adding the column like qquuid to the model that is handling the files. For example:
Attachment.new(params[:qqfile], params[:qquuid])
After you save all the files, you can combine them (check the ruby File class to learn how to).
Attachment.where(qquuid: params[:qquuid]).combine_them_all
The above line can be put either in the create action at the end of it, with the condition stating that this is the last part (there are params with the total part number and the index number of the current part, that can be uset to determine that), or in the "finish" action, that you can use if you do
chunking:
success:
endpoint: "/upload/finish"
You will have to create a route (same way as shown above) and the action. This action will be triggered after the last part was send. If the file was too small to be parted, this will NOT get triggered, unless you set mandatory to "true".
The last thing, is the json respond. That part is simple, fine uploader expects you to respond (with json) that you received the file and everything went smoothly. If it won't get it, it will assume, something went wrong (you can read more about expected json in the uploader docs). What matters is that in case of failure, it will try to send failed part again (if autoRetry is set to true).
Now, for the view (haml):
#fine-uploader{"data- authenticity-token" => form_authenticity_token}
%script#template-name
Here goes the template
More about templating you can read in docs, but important thing is, don't use rails form (or simple form) for that. There is a way of connecting forms with fine uploader, but I wasn't able to make it work, and I've had no need of using the form, but if you need it, you can create a hidden field with the generated token, to identify it, and use it instead of qquuid to identify the files. You can provide it in params section the same way, you have provided CSRF token, and use it in the "create" action in the uploads controller.
And that's it. I hope it will help someone.
EDIT: There is an example app made by user Panczo posted in the comments
