错误(为nil:NilClass调用了私有方法“ select”):

时间:2019-03-11 02:41:54

标签: ruby-on-rails ruby ruby-on-rails-5.2

为什么会出现此错误?我该如何解决?

  

ActionView :: Template :: Error(调用了私有方法“ select”   nil:NilClass):

class MyformObject

  include ActiveModel::Model

  #validations


@form_structure =
  [
    {  name: :country, model: :car, field_type: :string },
    {  name: :street, model: :repair_center, field_type: :string }
  ]

  def get_model_from_name(name)
    model = @form_structure.select { |record| record[:name] == name }.first[:model]
  end  

  def type_for_attribute(name)
    get_model_from_name(name).to_s.capitalize.constantize.type_for_attribute
  end 

  def has_attribute?(name)
    get_model_from_name(name).to_s.capitalize.constantize.attributes.key?(name.to_s)
   end

def self.fields_of_model(model)
  form_structure.select { |record| record[:model] == model }.map { |record| record[:name] }
end

 end

更新版本:

  

错误:nil:NilClass def的未定义方法“ []”   get_model_from_name(名称)
        模型= self.class.form_structure.select {|记录| record [:name] == name} .first [:model]       结束

class MyformObject

  include ActiveModel::Model

  #validations


def self.form_structure 
  [
    {  name: :country, model: :car, field_type: :string },
    {  name: :street, model: :repair_center, field_type: :string }
  ]
end

  def get_model_from_name(name)
    model = self.class.form_structure.select { |record| record[:name] == name }.first[:model]
  end  

  def type_for_attribute(name)
    get_model_from_name(name).to_s.capitalize.constantize.type_for_attribute
  end 

  def has_attribute?(name)
    get_model_from_name(name).to_s.capitalize.constantize.attributes.key?(name.to_s)
   end

def self.fields_of_model(model)
  form_structure.select { |record| record[:model] == model }.map { |record| record[:name] }
end

def self.delegate_fields_to(*models)
      models.each do |model|
        fields_of_model(model).each do |attr|
          delegate attr.to_sym, "#{attr}=".to_sym, to: model
        end
      end
    end

 end

2 个答案:

答案 0 :(得分:3)

恕我直言,常量是处理该数组的好方法,因为它充满了硬编码的值,并且只包含两个元素。

因此您可以执行以下操作:

class MyformObject
  FORM_STRUCTURE = [
    { name: :country, model: :car, field_type: :string },
    { nname: :street, model: :repair_center, field_type: :string }
  ].freeze
  private_constant :FORM_STRUCTURE

  def get_model_from_name(name)
    FORM_STRUCTURE.select { |record| record[:name] == name }.first[:name]
  end 
end

p MyformObject.new.get_model_from_name(:country)
# [:country]

您可以看到常量不能被修改,只能在MyformObject范围内使用。

我删除了模型局部变量赋值,因为它未被使用。

答案 1 :(得分:1)

您可以这样尝试,但执行起来不太容易

  def get_model_from_name(name)
    model = form_structure.select { |record| record[:name] == name }.first[:model]
  end

  def form_structure
    [
      {  name: :country, model: :car, field_type: :string },
      {  name: :street, model: :repair_center, field_type: :string }
    ]
  end

为了获得更好的封装,可以将方法form_structure放在私有范围内。