ruby – 我可以为RSpec匹配器添加别名吗？

发布时间：2020-12-17 02:23:02 所属栏目：百科来源：网络整理

导读：我有两个与他们的名字完全相同的匹配器： RSpec::Matchers.define :be_the_downcased_version_of do |actual| match do |actual| @actual = actual @expected = expected @actual == @expected.downcase end failure_message do |actual| "Expected #{@actua

我有两个与他们的名字完全相同的匹配器：

RSpec::Matchers.define :be_the_downcased_version_of do |actual|
    match do |actual|
        @actual = actual
        @expected = expected

        @actual == @expected.downcase
    end

    failure_message do |actual|
        "Expected #{@actual.inspect} to be the downcased version of #{expected.inspect}.nIt was not: #{@actual.inspect}"
    end

    failure_message_when_negated do |actual|
        "Expected #{@actual.inspect} to not be the downcased version of #{expected.inspect}.nIt was: #{@actual.inspect}"
    end

    description do
        "be the downcased version of #{expected.inspect}"
    end
end

RSpec::Matchers.define :return_the_downcased_version_of do |actual|
    match do |actual|
        @actual = actual
        @expected = expected

        @actual == @expected.downcase
    end

    failure_message do |actual|
        "Expected #{@actual.inspect} to be the downcased version of #{expected.inspect}.nIt was not: #{@actual.inspect}"
    end

    failure_message_when_negated do |actual|
        "Expected #{@actual.inspect} to not be the downcased version of #{expected.inspect}.nIt was: #{@actual.inspect}"
    end

    description do
        "be the downcased version of #{expected.inspect}"
    end
end

我可以像使用Ruby别名方法一样对它们进行别名吗？

alias_method :foo_meth,:bar_meth

解决方法

是的,您可以为使用RSpec的匹配器DSL定义的匹配器添加别名.我知道这样做最方便的方法是在before块中重新打开示例上下文的类,并在那里为方法添加别名.

但首先,让我们清理你的匹配器.

>传递给Matchers.define的块采用预期值,而不是
实际值,作为其论点.
>您不需要那些实例变量;它们的值已经在块参数中可用.

在spec / support / be_the_downcased_version_of.rb中：

RSpec::Matchers.define :be_the_downcased_version_of do |expected|
  match do |actual|
    actual == expected.downcase
  end

  failure_message_for_should do |actual|
    "Expected #{actual.inspect} to be the downcased version of #{expected.inspect}.nIt was not: #{actual.inspect}"
  end

  failure_message_for_should_not do |actual|
    "Expected #{actual.inspect} to not be the downcased version of #{expected.inspect}.nIt was: #{actual.inspect}"
  end

  description do
    "be the downcased version of #{expected.inspect}"
  end

end

要在spec / spec_helper.rb中为该匹配器定义的方法添加别名：

config.before :each do
  class << self
    alias_method :return_the_downcased_version_of,:be_the_downcased_version_of
  end
end

这是另一种方法.我实际上不会这样做,因为它需要更多的样板,但它比以前的方法使用更少的魔力,因此它可能提供信息.只需在没有DSL的情况下实现匹配器并正常使用该方法.在spec / support / be_the_downcased_version_of.rb中：

alias_method :return_the_downcased_version_of,:be_the_downcased_version_of

def be_the_downcased_version_of(actual)
  BeTheDowncasedVersionOf.new actual
end

class BeTheDowncasedVersionOf
  def initialize(expected)
    @expected = expected
  end

  def matches?(actual)
    @actual = actual
    @actual == @expected.downcase
  end

  def failure_message_for_should
    "Expected #{@actual.inspect} to be the downcased version of #{@expected.inspect}.nIt was not: #{@actual.inspect}"
  end

  def failure_message_for_should_not
    "Expected #{@actual.inspect} to not be the downcased version of #{@expected.inspect}.nIt was: #{@actual.inspect}"
  end

  def description
    "be the downcased version of #{@expected.inspect}"
  end

end

（编辑：李大同）

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