Ruby-on-rails 未定义的方法“包括？” 对于 nil:NilClass，对向导 gem 进行了部分验证

undefined method `include?' for nil:NilClass with partial validation of wizard gem

提问by cyclopse87

I am trying to follow the guide for partial validation on object using the wizard gem, but I keep getting the error undefined method `include?' for nil:NilClass, cant understand what is wrong, have tried to follow the step by step instructions.

我正在尝试遵循使用向导 gem 对对象进行部分验证的指南，但我不断收到错误未定义的方法“包含？” 对于 nil:NilClass，无法理解有什么问题，已尝试按照分步说明进行操作。

The error in the log shows.

日志中的错误显示。

NoMethodError - undefined method `include?' for nil:NilClass:
app/models/property.rb:22:in `active_or_tenants?'

Here is my steps controller.

这是我的步骤控制器。

class Properties::BuildController < ApplicationController
  include Wicked::Wizard

  steps :tenant, :confirmed 

  def show
    @property = Property.find(params[:property_id])
    @tenants = @property.tenants.new(params[:tenant_id])
    render_wizard
  end

  def update
    @property = Property.find(params[:property_id])
    params[:property][:status] = step.to_s
    params[:property][:status] = 'active' if step == steps.last
    @property.update_attributes(params[:property])
    render_wizard @property
  end

  def create
    @property = current_user.properties.build(params[:property])
      logger.info @property.attributes
    if @property.save
        flash[:success] = "Tenant Added"
        redirect_to wizard_path(steps.second, :property_id => @property.id)
    else
        render 'edit'
    end
  end
end

Property.rb

属性文件

class Property < ActiveRecord::Base
  attr_accessible  :name, :address_attributes, :tenants_attributes, :property_id, :status
  belongs_to :user 

  has_one :address, :as => :addressable
  accepts_nested_attributes_for :address, :allow_destroy => true

  has_many :tenants 
  accepts_nested_attributes_for :tenants, :allow_destroy => true

  validates :name,        :presence => true
  validates :address,     :presence => true
  validates :tenants,     :presence => true, :if => :active_or_tenants?

  def active?
    status == 'active'
  end

  def active_or_tenants?
    status.include?('tenants') || active?
  end
end

Let me know if you need any other parts added to the question. Thanks in advance.

如果您需要在问题中添加任何其他部分，请告诉我。提前致谢。

采纳答案by MrYoshiji

From my comments:

从我的评论：

The statusis an attribute of your Property model. It can be nilwhich raises an error in certain cases:

该status是你的属性模型的属性。nil在某些情况下可能会引发错误：

undefined method include?' for nil:NilClass

It is actually trying to compare nilto 'tenants'(String).

它实际上是在尝试nil与'tenants'(String)进行比较。

To fix that, you can use an empty string to be compared if statusis nil,

要解决这个问题，您可以使用一个空字符串进行比较，如果status是nil，

# an example (you can try in your IRB console):
nil || "No value"
# => returns "No value"

in your case:

在你的情况下：

def active_or_tenants?
  status.to_s.include?('tenants') || active?
end

nil.to_sreturn an empty string. Which solves your problem ;)

nil.to_s返回一个空字符串。这解决了你的问题;)

---

---

Actually, the methods to_s, to_i, to_fetc. are often used to remove the possible nil:

其实，方法to_s，to_i，to_f等经常被用来去除可能的nil：

# in ruby console:
2.3.3 :018 > nil.to_i
# => 0 
2.3.3 :019 > nil.to_f
# => 0.0 
2.3.3 :020 > nil.to_s
# => "" 
2.3.3 :021 > nil.to_a
# => [] 

回答by Omar Bahareth

In Ruby 2.3 you can use the safe navigation operator, which will simply return nil when your object is nil and it won't throw an error.

在 Ruby 2.3 中，您可以使用安全导航操作符，当您的对象为 nil 时它只会返回 nil 并且不会抛出错误。

def active_or_tenants?
  status&.include?('tenants') || active?
end

回答by Toma? Zaman

There is another solution to this, you might want to set a default state upon object creation, preferable in the migration.

还有另一种解决方案，您可能希望在创建对象时设置默认状态，在迁移中更可取。

class AddStatusToProperties < ActiveRecord::Migration
  def change
    create_table :projects do |t|
      t.string :status, default: 'new'
    end
  end
end

Following this you'll never have nilfor your state

在此之后，您将永远不会拥有nil您的州