Rails的ActiveRecord保存错误未定义的方法'[]'为零：NilClass

Question

我试图保存我的模型对象导轨时出现错误。让我说，我没有使用数据库迁移，并使用预先存在的数据库与轨道。 这里是我的模型类：

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 

这里是我的数据库架构：

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 

这是我为我的控制器代码：

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 

上的个人资料时发生错误。保存'方法。下面是相关堆栈跟踪：

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' 

错误说：“未定义的方法`[]”为无：NilClass”

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 

现在你可以使用它像：

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

顺便说一句，你hash_rep方法是没有多大用处的，请尝试：

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

图片的标题说明：

• 自你遵循约定，你不需要添加th OSE线，你可以删除它们：self.table_name = 'profiles'，self.primary_key = 'id'

• 提防哈希，似乎你不约字符串或符号键照顾，但他们是不一样的

• 有写更优雅的方式是你的方法，但我已经把它简单，因为它没有必要在这个阶段

Answer 2

在新的方法中，你应该改变这些是符号，从：

@first_name = attributes[first_name] 
@last_name = attributes[last_name] 
@location = attributes[location] 

要：

@first_name = attributes[:first_name] 
@last_name = attributes[:last_name] 
@location = attributes[:location] 

而且，你不必在一个选项哈希通过？因为你不使用它。

Answer 3

一个更好的方法来设置轨道默认属性来阐述是通过回调：

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

    attr_accessor :password # is a virtual attribute 

    after_initialize do 
    if new_record? 
     # values will be available for new record forms. 
     self.status = status || "Hi" 
     self.game_status = game_status || "Playing some game..." 
    end 
    end 

    before_validation(on: :create) do 
    self.salt = SecureRandom.hex 
    self.password_hash = Password.create(password + salt).to_s 
    end 

    # Yuck. use http://apidock.com/rails/ActiveModel/Serialization/serializable_hash 
    def hash_rep 
    serializable_hash(only: [:id, :username, :password_hash, :salt, :location, :status, :game_status]) 
    end 

end 

您不需要为ActiveRecord列创建访问器。您无需指定table和primary_key。 Rails指出了你。另外你真的不想重新定义initialize，因为活跃的记录在那里有一堆。

您的控制器也缺少标记。 Rails通常在资源名称下嵌套参数。 - 如果您使用Rails 4，你会whitelist和分配参数：

class ProfileController < ApplicationController 

    def new 
    @profile = Profile.new 
    end 

    def register 
    @profile = Profile.new(create_params) 
    if @profile.save 
     redirect_to @profile 
    else 
     render action: :new 
    end 
    end 

    private 
    def create_params 
    params.require(:profile).allow(:username, :password, : first_name :last_name :location) 
    end 
end