文字のみの投稿の際、ハッシュタグをつけて保存したいがundefined method `find_by' for ActiveRecord::AttributeMethodsのエラー。

前提・実現したいこと

railsまだまだ勉強中の者です。
今文字や画像などを投稿する際、ハッシュタグ機能を付けようとしています。
画像投稿の際は、ちゃんとエラーも起こらずハッシュタグ機能をつけることができました。

発生している問題・エラーメッセージ

エラーメッセージ
undefined method `find_by' for ActiveRecord::AttributeMethods::Write:Module

after_create do
    write = Write.find_by(id: self.id)
    tags  = self.summary.scan(/[#＃][\w\p{Han}ぁ-ヶｦ-ﾟー]+/)
 　　　tags.uniq.map do |t|
      tag = Tag.find_or_create_by(name: t.downcase.delete('#'))
      write.tags << tag
end

#エラーとなっている部分はwrite = Write.find_by(id: self.id)

class Write < ApplicationRecord
  belongs_to :user
  has_many :comments
  has_many :likes, dependent: :destroy
  has_many :likes_users, through: :likes, source: :user


  has_many :post_tags, dependent: :destroy
  has_many :tags, through: :post_tags

  after_create do

    write = Write.find_by(id: self.id)
    tags  = self.summary.scan(/[#＃][\w\p{Han}ぁ-ヶｦ-ﾟー]+/)
    tags.uniq.map do |t|
      tag = Tag.find_or_create_by(name: t.downcase.delete('#'))
      write.tags << tag
    end
  end


end

class WritesController < ApplicationController

  before_action :move_to_index, except: [:index, :show]

  def index
    @write = Write.includes(:user).order("created_at DESC")
  end

  def new
    @write = Write.new
  end

  def create
    @write = Write.new(write_params)
    if @write.user_id = current_user.id
    @write.save
    redirect_to action: :index
    end
  end

  def destroy
    write = Write.find(params[:id])
    if write.user_id == current_user.id
      write.destroy
    end
  end

  def edit
    @writes = Write.find(params[:id])
    if @writes.user_id != current_user.id
      redirect_to "/writes"
    end
  end

  def update
    write = Write.find(params[:id])
    if write.user_id == current_user.id
      write.update(write_params)
    end
  end

  def show
    @writes = Write.find(params[:id])
    @comment = Comment.new
    @comments = @writes.comments.order(created_at: :desc)
    @com = "write"
    @like = Like.new
  end

    private
    def write_params
      params.require(:write).permit(:title, :content, :summary, :tag_ids)
    end


    def move_to_index
      redirect_to action: :index unless user_signed_in?
    end

end

#投稿の際のform
<div class="posts-wrapper-content">
　<div class="preview" id="image">
  <%= form_with model: @write, local: true  do |w| %>
  <div class="write-content">
    <%= w.text_area :content, placefolder: "story" %>
  </div>
  </div>
  <div class="information-content">
  <div class="info-cover">
  <div class="title-form">
  :タイトルを入力してください
  </div>
    <%= w.text_field :title %>
  <div class="content-wrapper">
  :内容を入力してください。
  </div>
    <%= w.text_area :summary, class: 'content-form' %>
    <%= w.submit "投稿する", class: 'send-button' %>
  <% end %>
  </div>
  </div>
</div>

class Image < ApplicationRecord

  belongs_to :user

  has_one_attached :image, dependent: :destroy

  has_many :likes, dependent: :destroy
  has_many :likes_users, through: :likes, source: :user

  has_many :comments


  has_many :post_tags, dependent: :destroy
  has_many :tags, through: :post_tags


  def image_type
    if image.attached? == false
      errors.add(:image, 'error message')
    end
  end

  after_create do

    image = Image.find_by(id: self.id)
    tags  = self.content.scan(/[#＃][\w\p{Han}ぁ-ヶｦ-ﾟー]+/)
    tags.uniq.map do |t|
      tag = Tag.find_or_create_by(name: t.downcase.delete('#'))
      image.tags << tag
    end
  end

  before_update do
    image = Image.find_by(id: self.id)
    image.tags.clear
    tags = self.caption.scan(/[#＃][\w\p{Han}ぁ-ヶｦ-ﾟー]+/)
    tags.uniq.map do |hashtag|
      tag = Tag.find_or_create_by(name: hashtag.downcase.delete('#'))
      image.hashtags << tag
    end
  end
end

class ImagesController < ApplicationController

  def new
    @image = Image.new
  end

  def index
    @images = Image.order("created_at DESC")
  end


  def create
    @image = Image.new(image_params)
    @image.user_id = current_user.id

    if @image.image.attached? == false
      @error = "画像ファイルを貼り付けてください"
      render :new
    else
      @image.save
      redirect_to action: :index
    end
  end


  def destroy
    image = Image.find(params[:id])
    if image.user_id == current_user.id
      image.destroy
    end
    redirect_to action: :index
  end


  def show
    @image = Image.find(params[:id])
    @user  = User.find(@image.user_id)
    @like = Like.new

    @comment = Comment.new
    @comments = @image.comments.order(created_at: :desc)

  end

  def edit
    @image = Image.find(params[:id])
  end

  def update
    @image = Image.find(params[:id])
    @image.update params.require(:image).permit(:title, :content, :image) # POINT
    redirect_to @image
  end

  private
  def image_params
    params.require(:image).permit(:title, :content, :image, :tag_ids)
  end

end