ruby-on-rails - Rails ActiveRecord 保存错误未定义方法 `[]' for nil :NilClass

Question

尝试在 Rails 中保存模型对象时出现错误。让我说一下，我没有使用数据库迁移，而是使用带有 Rails 的预先存在的数据库。 这是我的模型类:

require 'bcrypt'
require 'securerandom'
class Profile < ActiveRecord::Base
  include BCrypt

  self.table_name = 'profiles'
  self.primary_key = 'id'

  attr_accessor :id, :username, :password_hash, :salt, :first_name, :last_name, :location, :status, :game_status

  def initialize(attributes = {}, options = {})
    @username = attributes[:username]
    @salt = SecureRandom.hex
    @password_hash = Password.create(attributes[:password] + @salt).to_s
    @first_name = attributes[first_name]
    @last_name = attributes[last_name]
    @location = attributes[location]
    @status = "Hi"
    @game_status = "Playing some game..."
  end

  def hash_rep
    hash = {}
    hash['id'] = @id
    hash['username'] = @username
    hash['password_hash'] = @password_hash
    hash['salt'] = @salt
    hash['location'] = @location
    hash['status'] = @status
    hash['game_status'] = @game_status
    return hash
  end

end

这是我的数据库架构:

id             int Unsigned NOT NULL AUTO_INCREMENT
username       varchar(16)  NOT NULL
password_hash  tinytext     NOT NULL
salt           varchar(64)  NOT NULL
first_name     varchar(16)  NOT NULL
last_name      varchar(16)  NOT NULL
location       tinytext     NOT NULL
status         tinytext     NULL
game_status    tinytext     NULL

这是我的 Controller 代码:

  def register
    profile = Profile.new(:id => params[:id],
                          :username => params[:username],
                          :password => params[:password],
                          :first_name => params[:first_name],
                          :last_name => params[:last_name],
                          :location => params[:location])
    profile.save
    render_profile(profile)
  end

“profile.save”方法发生错误。这是相关的堆栈跟踪:

activerecord (4.2.0) lib/active_record/transactions.rb:375:in `clear_transaction_record_state'
activerecord (4.2.0) lib/active_record/transactions.rb:306:in `ensure in rollback_active_record_state!'
activerecord (4.2.0) lib/active_record/transactions.rb:306:in `rollback_active_record_state!'
activerecord (4.2.0) lib/active_record/transactions.rb:285:in `save'
app/controllers/profile_controller.rb:52:in `register'
actionpack (4.2.0) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (4.2.0) lib/abstract_controller/base.rb:198:in `process_action'

错误提示:“nil:NilClass 的未定义方法‘[]’”

Answer 1

require 'bcrypt'
require 'securerandom'
class Profile < ActiveRecord::Base
  include BCrypt

  self.table_name = 'profiles'
  self.primary_key = 'id'

  def hash_rep
    hash = {}
    hash['id'] = id
    hash['username'] = username
    hash['password_hash'] = password_hash
    hash['salt'] = salt
    hash['location'] = location
    hash['status'] = status
    hash['game_status'] = game_status
    hash
  end

  def self.build(args)
    new_profile = Profile.new
    new_profile.username = args[:username]
    salt = SecureRandom.hex
    new_profile.password_hash = Password.create(args[:password] + salt).to_s
    new_profile.first_name = args[:first_name]
    new_profile.last_name = args[:last_name]
    new_profile.location = args[:location]
    new_profile.status = "Hi"
    new_profile.game_status = "Playing some game..."
    new_profile
  end
end

现在你可以像这样使用它:

Profile.build({ username: 'foo' })

顺便说一句，你的 hash_rep 方法没那么有用，尝试一下:

profile = Profile.build({ username: 'foo' })
profile.attributes

旁注:

• 由于您遵循约定，因此不需要添加这些行，只需删除它们即可:self.table_name = 'profiles', self.primary_key = 'id'

• 小心哈希值，似乎您不关心字符串或符号键，但它们并不相同

• 有更优雅的方式来编写你的方法，但我保持简单，因为在这个阶段没有必要详细说明