ruby-on-rails - rails 中的 Controller 构造函数参数？

Question

我们如何在 Controller 的构造函数中注入(inject)参数或者 Rails 中依赖注入(inject)的原理是什么？

假设我需要将支付服务注入(inject) Controller 。在 .NET 世界中，我会使用 DI 框架，将其配置为为 IPaymentService 依赖项注入(inject) CreditPaymentService 实例。

在 rails 中，我们如何实现这一点？特别是对于测试和模拟？

我读到多个来源表明我们不需要任何 DI 框架来在 ruby​​ 中完成 DI 但我不知道如何为 Controller 做这件事？

谢谢!

// .NET
public class OrderController : Controller
{
    IPaymentService _paymentService;

    public OrderController(IPaymentService paymentService)
    {
        _paymentService = paymentService;
    }

    public object Pay(Order order)
    {       
        _paymentService.process(order.GetTotal());
    }
}

# Rails
class order_controller < ApplicationController

    def initialize(payment_service)
        @payment_service = payment_service
    end 

    def pay
        order = request.parameters(:order)
        @payment_service.process(order)
    end
end

Answer 1

试一试:

class OrdersController < ApplicationController

  def pay
    # you'll need to define payment_params elsewhere in the controller
    PaymentService.call(payment_params)
  end

end

PaymentService 只是一个普通的旧 ruby​​ 对象:

class PaymentService

  attr_accessor *%w(
    options
  ).freeze

  class << self 

    def call(options={})
      new(options).call
    end

  end # Class Methods

  #==========================================================================
  # Instance Methods
  #==========================================================================

    def intialize(options={})
      @options = options
    end

    def call 
      # do stuff
      # return something
    end

end

我个人喜欢让 call 成为一个类方法，这样我就不必做:

PaymentService.new(payment_params).call

这对我来说看起来不太干净。但是，这纯粹是个人喜好问题。

你可以把它放在:

app
 |- ...
 |- services
 |   |- payment_service.rb
 |- ...

这将导致服务自动加载，您将不必使用 config.autoload_paths。

测试服务很简单(这就是重点，不是吗？)。这是一个 rspec 示例:

require 'rails_helper'

RSpec.describe PaymentService do
  before(:all) do
    @method_name = "call"
  end
  describe "#call" do
    it "responds" do
      expect(described_class.respond_to?(@method_name)).to be_truthy
    end
    context "when using good params" do 
      before(:each){ @params = good_params }
      it "does something" do
        expect(calling_the_service).to do_something
      end
    end
  end
end

def calling_the_service
  described_class.send method_name, params
end

def good_params
  {some: :arguments}
end

def params
  @params 
end

def method_name
  @method_name
end

事实上，我做的更像是:

class ApplicationController < ActionController::Base
  # I have a custom module that lets me make this call. Among other things,
  # it creates the call_service method on all controllers. 
  acts_as calling: :services 
end

OrdersController 现在知道如何call_service:

class OrdersController < ApplicationController

  def pay
    # Given the acts_as calling: :services call, above, the OrdersController 
    # knows how to inspect the SERVICE_DETAIL constant on PaymentService 
    # and construct the appropriate arguments. In this case, passing in 
    # something like {current_user: 1}
    call_service PaymentService
  end

end

我将一些东西移动到 ServiceBase 中:

class ServiceBase 

  attr_accessor *%w(
    options
  ).freeze

  class << self 

    def call(options={})
      new(options).call
    end

  end # Class Methods

  #======================================================================
  # Instance Methods
  #======================================================================

    def intialize(options={})
      @options = options
    end

  private 

    # This method reads the REQUIRED_ARGS AND REQUIRED_VALUES constants 
    # and determines whether a valid service call was made. It also logs
    # errors so that I can go back and see failures.
    def good_to_go?
      # some stuff
    end

    def decorated_options
      @decorated_options ||= OptionsDecorator.new(options)
    end

end

现在我以常量形式在服务上声明一些元数据。它们本质上定义了服务的接口(interface):

class PaymentService < ServiceBase

  SERVICE_DETAILS = [
    {current_user: [:id]}
  ].freeze

  REQUIRED_ARGS = %w(
    current_user
  ).freeze

  REQUIRED_VALUES = %w(
    current_user_id
  ).freeze

  delegate *%w(
    current_user_id
  ), to: :decorated_options

  #======================================================================
  # Instance Methods
  #======================================================================

    def call 
      raise unless good_to_go?
      # do stuff
      # return something
    end

end