更新使用活动存储的用户记录不起作用

Question

我正在练习使用Railsactive_storage。所以我创建了一个只有一个模型的应用程序 -User.User有两个主要的数据库列 -username和profile_pic。然后通过active_storage它has_many_attached :avatars.我正在实现的功能是，before_validation用户记录中，我想分配附加的第一个头像(用户可以在注册时上传许多图像(作为profile_pic。这是完整的模型

class User < ApplicationRecord
include Rails.application.routes.url_helpers
has_many_attached :avatars
validates :username, presence: true
before_validation :assign_profile_pic
def change_profile_pic
self.profile_pic = rails_blob_path(avatars.last, only_path: true)
save
end
private
def assign_profile_pic
self.profile_pic = rails_blob_path(avatars.first, only_path: true)
end
end

这是用户控制器

class V1::UsersController < ApplicationController
# include Rails.application.routes.url_helpers
def show
user = User.find_by(username: params[:username])
if user.present?
render json: success_json(user), status: :ok
else
head :not_found
end
end
def create
user = User.new(user_params)
if user.save
render json: success_json(user), status: :created
else
render json: error_json(user), status: :unprocessable_entity
end
end
def update
user = User.find_by(username: params[:username])
if user.update(user_params)
user.change_profile_pic
render json: success_json(user), status: :accepted
else
render json: error_json(user), status: :unprocessable_entity
end
end
def avatar
user = User.find_by(username: params[:user_username])
if user&.avatars&.attached?
redirect_to rails_blob_url(user.avatars[params[:id].to_i])
else
head :not_found
end
end
private
def user_params
params.require(:user).permit(:username, avatars: [])
end
def success_json(user)
{
user: {
id: user.id,
username: user.username
}
}
end
def error_json(user)
{ errors: user.errors.full_messages }
end
end

创建用户不是问题。它按预期工作，它在创建时自动分配user.avatars.first作为user.profile_pic。问题发生在update部分。您会看到我在成功更新后调用change_profile_pic用户方法(在users_controller中(。问题是user.profile_pic永远不会更新。我已经调试了很多次，user_params没有任何问题。我错过了什么？

Answer 1

before_validation每次在before_save之前运行。您设置一次，然后再次设置。请参阅此处的顺序：https://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

如果您只是更改个人资料图片，请避免使用assign_profile_pic进行验证。一个干净的方法是使用ActiveModel::AttributeMethods

class User < ApplicationRecord
include Rails.application.routes.url_helpers
has_many_attached :avatars
validates :username, presence: true
before_validation :assign_profile_pic, unless: :changing_profile_pic?
attribute :changing_profile_pic, :boolean, default: false 
def change_profile_pic
self.profile_pic = rails_blob_path(avatars.last, only_path: true)
self.changing_profile_pic = true 
save
end
private
def assign_profile_pic
self.profile_pic = rails_blob_path(avatars.first, only_path: true)
end
end