Sending files to a Rails JSON API

I was actually having a terrible time with this question yesterday to do something very similar. In fact, I wrote the question: Base64 upload from Android/Java to RoR Carrierwave

What it came down to was creating that uploaded image object in the controller and then injecting it back into the params.

For this specific example, we are taking a base64 file (which I assume you have, as JSON doesn’t support embeded files) and saving it as a temp file in the system then we are creating that UploadedFile object and finally reinjecting it into the params.

What my json/params looks like:

picture {:user_id => "1", :folder_id => 1, etc., :picture_path {:file => "base64 awesomeness", :original_filename => "my file name", :filename => "my file name"}}

Here is what my controller looks like now:

  # POST /pictures
  # POST /pictures.json
  def create

    #check if file is within picture_path
    if params[:picture][:picture_path]["file"]
         picture_path_params = params[:picture][:picture_path]
         #create a new tempfile named fileupload
         tempfile = Tempfile.new("fileupload")
         tempfile.binmode
         #get the file and decode it with base64 then write it to the tempfile
         tempfile.write(Base64.decode64(picture_path_params["file"]))

         #create a new uploaded file
         uploaded_file = ActionDispatch::Http::UploadedFile.new(:tempfile => tempfile, :filename => picture_path_params["filename"], :original_filename => picture_path_params["original_filename"]) 

         #replace picture_path with the new uploaded file
         params[:picture][:picture_path] =  uploaded_file

    end

    @picture = Picture.new(params[:picture])

    respond_to do |format|
      if @picture.save
        format.html { redirect_to @picture, notice: 'Picture was successfully created.' }
        format.json { render json: @picture, status: :created, location: @picture }
      else
        format.html { render action: "new" }
        format.json { render json: @picture.errors, status: :unprocessable_entity }
      end
    end
  end

The only thing left to do at this point is to delete the tempfile, which I believe can be done with tempfile.delete

I hope this helps with your question! I spent all day looking for a solution yesterday, and everything I have seen is a dead end. This, however, works on my test cases.