ruby - 更改 described_class.new 参数的值

Question

我有以下代码:

require 'command'

describe Command do
  subject(:command) { described_class.new(input, robotic_rover) }

  let(:robotic_rover) do
    double(:robotic_rover, position: '0 0 N',
                           move: '0 1 N',
                           right_turn: '0 0 E',
                           left_turn: '0 0 W')
  end

  describe 'advance command' do
    let(:input) { 'M' }

    describe 'initialization' do
      it 'alters a rovers position' do
        expect(command.position_change).to eq robotic_rover.move
      end
    end
  end

  describe 'right command' do
    let(:input) { 'R' }

    describe 'initialization' do
      it 'alters a rovers direction' do
        expect(command.position_change).to eq robotic_rover.right_turn
      end
    end
  end

  describe 'left command' do
      let(:input) { 'L' }

    describe 'initialization' do
      it 'alters the rovers direction' do
        expect(command.position_change).to eq robotic_rover.left_turn
      end
    end
  end
end

在每个初始描述 block (高级命令、右命令和左命令)中，我试图定义传递给 described_class.new(input , robotic_rover) 和 let。

发生的情况是只有最后一个测试(左命令)通过，而前两个测试(高级命令和右命令)失败并显示:

 Failure/Error: expect(command.position_change).to eq robotic_rover.right_turn

   expected: "0 0 E"
        got: nil

如果我从前两个测试中的每一个中删除 let，那么它们会失败:

 Failure/Error: subject(:command) { described_class.new(input, robotic_rover) }

 NameError:
   undefined local variable or method `input' for #<RSpec::ExampleGroups::Command::AdvanceCommand::Initialization:0x007f90cc14f758>

谁能帮我更改每个描述 block 的 initialize 参数的值？

代码

此代码的目的是从多个 if 中重构它，但现在，这就是我所拥有的。

class Command
  attr_reader :input, :robotic_rover

  def initialize(input, robotic_rover)
    @input         = input
    @robotic_rover = robotic_rover
  end

  def position_change
    robotic_rover.move if input == 'M'
    robotic_rover.right_turn if input == 'R'
    robotic_rover.left_turn if input == 'L'
  end
end

Answer 1

我们在 #position_change 方法中缺少每个条件的 return。

what is the point of return in Ruby?

class Command
  attr_reader :input, :robotic_rover

  def initialize(input, robotic_rover)
    @input         = input
    @robotic_rover = robotic_rover
  end

  def position_change
    return robotic_rover.move if input == 'M'
    return robotic_rover.right_turn if input == 'R'
    return robotic_rover.left_turn if input == 'L'
  end
end

describe Command do
  let(:instance) { described_class.new(input, robotic_rover) }

  let(:robotic_rover) do
    double(
      "RoboticRover",
      position: '0 0 N',
      move: '0 1 N',
      right_turn: '0 0 E',
      left_turn: '0 0 W'
    )
  end

  describe '#position_change' do
    subject(:position_change) { instance.position_change }

    context 'when advance command' do
      let(:input) { 'M' }

      it 'alters a rovers position' do
        expect(position_change).to eq robotic_rover.move
      end
    end

    context 'when right command' do
      let(:input) { 'R' }

      it 'alters a rovers direction' do
        expect(position_change).to eq robotic_rover.right_turn
      end
    end

    context 'when left command' do
      let(:input) { 'L' }

      it 'alters the rovers direction' do
        expect(position_change).to eq robotic_rover.left_turn
      end
    end
  end
end