How can I prevent duplicate image attachments in my Rails pins controller?

I'm encountering an issue where creating or updating a pin results in two copies of each image being attached.

I suspect that the problem arises because images are being attached twice – once automatically via the permitted parameters in pin_params and again manually within my controller actions. I believe the issue is in the controller, and I need help preventing duplicate attachments until I implement a way to remove individual images.

Below is the current code for my pins controller and the _pin.erb view:

RUBYCopied
class PinsController < ApplicationController
  before_action :set_pin, only: %i[show edit update destroy upvote downvote]
  before_action :authenticate_user!, except: %i[index show]
  before_action :authorize_user!, only: %i[edit destroy]

  # GET /pins or /pins.json
  def index
    @pins = Pin.all.order("created_at DESC")
  end

  # GET /pins/1 or /pins/1.json
  def show
  end

  # GET /pins/new
  def new
    @pin = current_user.pins.build
  end

  # GET /pins/1/edit
  def edit
  end

  # POST /pins or /pins.json
  def create
    @pin = current_user.pins.build(pin_params)

    # Ensure that at least one image is attached
    if params[:pin][:images].present?
      params[:pin][:images].each do |image|
        # Ensure image is an actual file
        if image.is_a?(ActionDispatch::Http::UploadedFile)
          # Read the image content once to calculate checksum
          image_content = image.read
          checksum = Digest::SHA256.hexdigest(image_content)

          # Check if any existing image blob already has this checksum
          unless @pin.images.any? { |img| img.blob.checksum == checksum }
            # Attach image only if it's not already attached
            @pin.images.attach(io: StringIO.new(image_content), filename: image.original_filename, content_type: image.content_type)
          end
        end
      end
    else
      flash.now[:alert] = "Please attach at least one image."
      render :new and return
    end

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

  # PATCH/PUT /pins/1 or /pins/1.json
  def update
    if @pin.user == current_user && @pin.update(pin_params)
      # Reattach new images if provided, avoiding duplicates
      if params[:pin][:images].present?
        params[:pin][:images].each do |image|
          if image.is_a?(ActionDispatch::Http::UploadedFile)
            # Read the image content once to calculate checksum
            image_content = image.read
            checksum = Digest::SHA256.hexdigest(image_content)

            # Check if any existing image blob already has this checksum
            unless @pin.images.any? { |img| img.blob.checksum == checksum }
              # Attach image only if it's not already attached
              @pin.images.attach(io: StringIO.new(image_content), filename: image.original_filename, content_type: image.content_type)
            end
          end
        end
      end

      redirect_to @pin, notice: "Pin was successfully updated."
    else
      render :edit, status: :unprocessable_entity
    end
  end

  # DELETE /pins/1 or /pins/1.json
  def destroy
    if @pin.user == current_user
      @pin.destroy
      redirect_to pins_path, notice: "Pin was successfully destroyed."
    else
      redirect_to root_path, notice: "Not your pin!"
    end
  end

  # Upvote the pin
  def upvote
    if !@pin.votes_for.exists?(voter: current_user)
      @pin.upvote_by current_user
    else
      flash[:alert] = "You have already upvoted this pin."
    end
    redirect_back(fallback_location: pin_path(@pin))
  end

  # Downvote the pin
  def downvote
    if !@pin.votes_against.exists?(voter: current_user)
      @pin.downvote_from current_user
    else
      flash[:alert] = "You have already downvoted this pin."
    end
    redirect_back(fallback_location: pin_path(@pin))
  end

  private

  # Set the pin based on its ID
  def set_pin
    @pin = Pin.find(params[:id])
  end

  # Only allow a list of trusted parameters through
  def pin_params
    params.require(:pin).permit(:title, :description, images: [])
  end

  # Authorize user to edit or destroy their own pin
  def authorize_user!
    redirect_to root_path, notice: "Not your pin!" if @pin.user != current_user
  end
end

_pin.erb

ERBCopied
<div id="<%= dom_id(pin) %>">
  <div class="grid" data-masonry='{ "itemSelector": ".grid-item", "columnWidth": 200, "gutter": 10 }'>
    <% if pin.images.count == 1 %>
      <div class="single-image-container">
        <%= link_to pin do %>
          <div class="grid-item single-image">
            <p class="text-center text-warning bg-white border border-dark">
              <%= image_tag(pin.images.first.variant(resize_to_limit: [300, 300])) %>
            </p>
          </div>
        <% end %>
      </div>
    <% else %>
      <% pin.images.each do |image| %>
        <%= link_to pin do %>
          <div class="grid-item">
            <p class="text-center text-warning bg-white border border-dark">
              <%= image_tag(image.variant(resize_to_limit: [300, 300])) %>
            </p>
          </div>
        <% end %>
      <% end %>
    <% end %>
  </div>
</div>