undefined method `resize_to_limit' for という内容のエラーが出てしまう。

前提・実現したいこと

Ruby on Railsで自分の欲しいものを記録するインスタグラムのようなアプリを作っています。
gemのcarriewaveとminimagicを導入し、実装中なのですが上手く保存が出来ずundefined method `resize_to_limit' forというエラーが発生してしまいました。
このエラーを改善したいです。

発生している問題・エラーメッセージ

NoMethodError in PostsController#create
undefined method `resize_to_limit' for #<ImageUploader:0x00007fe07ed77d08>
Extracted source (around line #8):

  def create
    Post.create(post_params)
  end
  
  private


Application Trace | Framework Trace | Full Trace
app/controllers/posts_controller.rb:8:in `create'
Request
Parameters:

{"authenticity_token"=>"2OXVrHt1xUU0t3BGMWRRdwj2cFu0nUa37mmEMSCJB7JA7pe3I8h/97UiprBi5B1p9HIY4HOO2SsdEKOEbDV6AA==",
 "post"=>
  {"img"=>
    #<ActionDispatch::Http::UploadedFile:0x00007fe07ed5f488
     @content_type="image/jpeg",
     @headers="Content-Disposition: form-data; name=\"post[img]\"; filename=\"IMG_6632.jpeg\"\r\n" + "Content-Type: image/jpeg\r\n",
     @original_filename="IMG_6632.jpeg",
     @tempfile=#<File:/var/folders/8h/t40pc8b131bbmlmsmnk6w2_r0000gn/T/RackMultipart20201208-8860-1via5s0.jpeg>>},
 "commit"=>"アップロードする"}

20201208031516_add_img_to_posts.rb

class AddImgToPosts < ActiveRecord::Migration[6.0]
  def change
    add_column :posts, :img, :string
  end
end

routes.rb

Rails.application.routes.draw do
  get 'items/download/:id', to: "items#download", as: "download_img"
  resources :posts
  devise_for :users
  root to: 'items#index'
  resources :items do
    resources :comments, only: :create
    collection do
      get 'search'
    end
  end
  resources :users, only: :show
end

_form.html.haml

= form_with(model: item, local: true) do |form|
  = form.text_field :image, placeholder: "Image Url"
  = form.text_area :memo, pleaceholder: "memo", rows: "10"
  = form.submit "SEND"

= form_for @post do |f|
  = f.file_field :img
  = f.submit 'アップロードする'

image_uploader.rb

class ImageUploader < CarrierWave::Uploader::Base
  # Include RMagick or MiniMagick support:
  # include CarrierWave::RMagick
  include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url(*args)
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process scale: [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  process resize_to_limit: [700, 700]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_whitelist
    %w(jpg jpeg gif png)
  end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end
end

post.rb

class Post < ApplicationRecord
  mount_uploader :img, ImageUploader
end

item.rb

class Item < ApplicationRecord
  validates :memo, presence: true
  belongs_to :user
  has_many :comments

  def self.search(search)
    if search != ""
      Item.where('memo LIKE(?)', "%#{search}%")
    else
      Item.all
    end
  end

  
end

posts_controller.rb

class PostsController < ApplicationController

  def new
    @post = Post.new(post_params)
  end

  def create
    Post.create(post_params)
  end
  
  private

  def post_params
    params.require(:post).permit(:img)
  end

end

items_controller.rb

class ItemsController < ApplicationController

  before_action :set_item, only: [:edit, :show]
  before_action :move_to_index, except: [:index, :show, :search]

  def index
    @items = Item.includes(:user).order("created_at DESC")
  end

  def new
    @item = Item.new
    @post = Post.new(post_params)
  end

  def create
    Item.create(item_params)
  end

  def destroy
    item = Item.find(params[:id])
    item.destroy
  end

  def edit
  end

  def update
    item = Item.find(params[:id])
    item.update(item_params)
  end

  def show
    @comment = Comment.new
    @comments = @item.comments.includes(:user)
  end

  def search
    @items = Item.search(params[:keyword])
  end

  def download
    send_data(@post.img.read,:filename=>@post.img_identifier)
  end

  private
  def item_params
    params.require(:item).permit(:image, :memo).merge(user_id: current_user.id)
  end

  def set_item
    @item = Item.find(params[:id])
  end

  def move_to_index
    unless user_signed_in?
      redirect_to action: :index
    end
  end

  def  post_params
    params.permit(:img)
  end
end