Rspec - 覆盖 method_missing 和 respond_to_missing 后的参数错误答案

【问题标题】：Rspec - Argument error after overwriting method_missing and respond_to_missingRspec - 覆盖 method_missing 和 respond_to_missing 后的参数错误
【发布时间】：2021-07-02 14:16:03
【问题描述】：

我有一个控制器，我想为其编写 rspec

results_controller.rb

 class Api::V1::ResultsController < Api::V1::ApplicationController
   before_action :devices
   include DataHelper

  def show
    results = get_dr_results
    render json: { data: results }
  end
  
  private

  def get_dr_results
    program_ids = method_defined_in_crucible_helper
  end
end

module DataHelper
  include Cruciblehelper
  
 def method_missing(method_name, *args, &block)
   if condition
    do_something  
  else
    super.method_missing(method_name, *args, &block)
  end
end

def respond_to_missing?
  true
end
end

module CrucibleHelper
  def method_defined_in_crucible_helper
  end
end

现在在我的 rspec 中，我尝试模拟方法 method_defined_in_crucible_helper。

describe Api::V1::DrResultsController, type: :controller do
  describe 'GET #show' do
    before do
    allow_any_instance_of(CrucibleHelper).to receive(:method_defined_in_crucible_helper) { [utility_program.id, utility_program2.id] }
  end

  context 'returns data' do
    context 'returns expected events' do
      it 'should return success response with expected events' do
        get :show
      expect(JSON.parse(response.body)).to eq(expected_response)
    end
  end

我得到了

     Failure/Error:
   def respond_to_missing?
     true
   end
 
 ArgumentError:
   wrong number of arguments (given 2, expected 0)
 # ./app/helpers/data_helper.rb:72:in `respond_to_missing?'

如果我注释掉 respond_to_missing？方法，然后我的规格执行正常。有人可以帮我解决这个错误吗？

【问题讨论】：

def respond_to_missing?(method_name, include_private = false)
嗨@LamPhan，请添加您的评论作为详细答案，因为这对我有用。

标签： ruby-on-rails rspec method-missing

【解决方案1】：

Ruby Delegator#respond_to_missing? 是负责返回缺失的方法是否能够被对象处理的方法，它有两个参数：missing method name 和选项include_private。

最佳做法是：always define respond_to_missing? when overriding method_missing。

但是我不喜欢你申请的方式，背后的原因是最小惊喜规则，看看：

class DataHelper
 def method_missing(method_name, *args, &block)
   if method_name.to_s.start_with?('delegate')
    puts "a delegate method"
   else
    super
   end
 end

 def respond_to_missing?(method_name, include_private = false)
   true
 end
end

d = DataHelper.new
d.respond_to?(:answer) # true
d.answer # `method_missing': undefined method `answer' ... SURPRISE

如您所见，d 响应他可以负责 answer 方法，但是当调用该方法时，会引发 method_missing 错误。

因此，您需要将method_missing 和respond_to_missing? 匹配在一起：

class DataHelper
 def method_missing(method_name, *args, &block)
   if can_handle?(method_name)
    puts "a delegate method"
   else
    super
   end
 end

 def respond_to_missing?(method_name, include_private = false)
   return true if can_handle?(method_name)
   super
 end
 
 private

 def can_handle?(method_name)
   method_name.to_s.start_with?('delegate')
 end
end

d = D.new
d.respond_to?(:delegate_answer) # true
d.delegate_answer # delegate method
d.respond_to?(:answer) # false
d.answer # error

【讨论】：