堆栈级别太深

Question

您好我收到了"Stack level too deep"错误,我很确定它是从这个模型生成的.我知道它与递归调用有关,但到目前为止我无法找到它,谢谢.

class Character < ActiveRecord::Base

  # Associations
  belongs_to :user

  # Validations
  validates :name, :presence => true, :uniqueness => true, :length => 
  { minimum: 2, maximum: 20 }, format: { with: /\A[a-zA-Z]+\Z/ }
  validates :race, :presence => true
  validates :class, :presence => true
  validates :user, :presence => true

  def self.races
    ["Human", "Dwarf", "Elven", "Orc", "Undead", "Demon"]
  end

  def self.classes
    {
      :fighter => {strength: 4, endurance: 3, dexterity: -2, charisma: -2, wisdom: -2, intelligence: -3}, 
      :thief   => {strength: -3,endurance: 2, dexterity: 4, charisma: 2, wisdom: -2, intelligence: 0}, 
      :magi    => {strength: -3, endurance: -2, dexterity: -2, charisma: 2, wisdom: 3, intelligence: -3}, 
      :ranger  => {strength: -2, endurance: 2, dexterity: 2, charisma: 0, wisdom: -3, intelligence: 0}, 
      :cleric  => {strength: 2,endurance: 2, dexterity: -3, charisma: -2, wisdom: 3, intelligence: 2}
    }
  end

  def set_class(_class)
    _attributes = Character.classes[_class.downcase]
    transaction do
      self.class = _class.downcase
      _attributes.each do |name, value|
        self.name += value
      end
      self.save
    end
  end
end

服务器日志:

Started GET "/characters/new" for 127.0.0.1 at 2014-04-04 01:54:14 +0200
  [1m[36mActiveRecord::SchemaMigration Load (0.8ms)[0m  [1mSELECT "schema_migrations".* FROM "schema_migrations"[0m
Processing by CharactersController#new as HTML
  [1m[35mUser Load (1.5ms)[0m  SELECT "users".* FROM "users" WHERE "users"."id" = 1 ORDER BY "users"."id" ASC LIMIT 1
  Rendered shared/_error_messages.html.erb (3.8ms)
  Rendered characters/new.html.erb within layouts/application (38.1ms)
Completed 500 Internal Server Error in 199ms

SystemStackError - 堆栈级别太深:

activerecord (4.0.2) lib/active_record/attribute_methods/read.rb:85:in `'

Answer 1

您的代码有三个问题:

1. 你class用作属性,
2. 你是混乱:symbols和"String".downcase,
3. 你正在使用self.name(属性)认为它是一个不同的二传手.

类

不要用class.这是一个保留的关键字.
这些线条会让ruby非常困惑:

validates :class, :presence => true

self.class = _class.downcase

另外,我假设class您的数据库表中有一列.你应该把它重命名为character_class或者像rpg_class.

符号和字符串

您的self.classes方法返回Hash其键是符号的方法.然而,稍后您尝试使用字符串访问它:

_attributes = Character.classes[_class.downcase]

虽然:foobar.downcase确实无能为力,但您无法访问这些值"Foobar".downcase.
要解决这个问题,您可以:

• 使用 Character.classes[_class.to_sym]
• 用一个 HashWithIndifferentAccess

无论如何,可以通过使用memoization来改进该方法.
目前,您正在为每次调用重新创建哈希哈希值.相反,您可以将其保存在变量中,并仅在第一次创建它.

def self.classes
  @char_classes ||= { fighter: { #...
end

或者,更好的是,使用常量:

CHAR_CLASSES = { #.....

def self.classes
  CHAR_CLASSES
end

名称

我看到你已经有了这个验证:

validates :name, :presence => true, :uniqueness => true, :length => { minimum: 2, maximum: 20 }, format: { with: /\A[a-zA-Z]+\Z/ }

这意味着你name在数据库表中有一个列,它应该是一个String匹配的特定格式(只有2到20之间的字母).

有了这个,让我们来看看这段代码:

_attributes.each do |name, value|
  self.name += value
end

在这个局部范围内,name是一个包含Symbol(例如:strength)并且value是a 的变量Fixnum.
当你这样做self.name += value,但是,你是分配Fixnum给对象属性 name.

我看不出你在哪里定义像strength=或的方法dexterity=.我假设他们是桌上的专栏.

在那种情况下,这应该工作:

self.public_send("#{name}=", value)
# or just 'send' if it's a private method