rspec - 如何使用 let！设置2个变量？答案

【问题标题】：rspec - how to use let! to setup 2 variables?rspec - 如何使用 let！设置2个变量？
【发布时间】：2014-01-19 04:03:28
【问题描述】：

我目前有：

describe 'least number of moves from x to y' do

  it 'has a populated chessboard' do
    @wp='white-pawn'
    @bp='black-pawn'

    expect(ChessBoard.new.populate_new_board).to eq [
      ['white-castle','white-knight','white-bishop','white-queen','white-king','white-bishop','white-knight','white-castle'],
      [@wp,@wp,@wp,@wp,@wp,@wp,@wp,@wp],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [@bp,@bp,@bp,@bp,@bp,@bp,@bp,@bp],
      ['black-castle','black-knight','black-bishop','black-king','black-queen','black-bishop','black-knight','black-castle']]
  end

没问题。
我想改用 let!，所以我尝试了：

describe 'least number of moves from x to y' do

  let!(:wp){'white-pawn'}
  let!(:bp){'black-pawn'}

  it 'has a populated chessboard' do
    expect(ChessBoard.new.populate_new_board).to eq [
      ['white-castle','white-knight','white-bishop','white-queen','white-king','white-bishop','white-knight','white-castle'],
      [@wp,@wp,@wp,@wp,@wp,@wp,@wp,@wp],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [@bp,@bp,@bp,@bp,@bp,@bp,@bp,@bp],
      ['black-castle','black-knight','black-bishop','black-king','black-queen','black-bishop','black-knight','black-castle']]
  end

但它失败了，因为我现在所有的 @bp 和 @wp 值都为零。

如何解决，即为期望编写正确的 let 语法？

【问题讨论】：

标签： ruby rspec let

【解决方案1】：

let! 设置的是本地方法，而不是实例变量，所以这行得通：

 it 'has a populated chessboard' do
    expect(ChessBoard.new.populate_new_board).to eq [
      ['white-castle','white-knight','white-bishop','white-queen','white-king','white-bishop','white-knight','white-castle'],
      [wp,wp,wp,wp,wp,wp,wp,wp],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [bp,bp,bp,bp,bp,bp,bp,bp],
      ['black-castle','black-knight','black-bishop','black-king','black-queen','black-bishop','black-knight','black-castle']]
  end

【讨论】：

【解决方案2】：

您需要使用wp 而不是@wp 和bp 而不是@bp，因为它们是方法，而不是实例变量：

describe 'least number of moves from x to y' do

  let!(:wp){'white-pawn'}
  let!(:bp){'black-pawn'}

  it 'has a populated chessboard' do

    expect(ChessBoard.new.populate_new_board).to eq [
      ['white-castle','white-knight','white-bishop','white-queen','white-king','white-bishop','white-knight','white-castle'],
      [wp,wp,wp,wp,wp,wp,wp,wp],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [nil,nil,nil,nil,nil,nil,nil,nil],
      [bp,bp,bp,bp,bp,bp,bp,bp],
      ['black-castle','black-knight','black-bishop','black-king','black-queen','black-bishop','black-knight','black-castle']]
  end
end

【讨论】：