Ruby 赋值方法不会收到 block ？

Question

我正在构建一个 DSL 并拥有这个模块

module EDAApiBuilder
  module Client

    attr_accessor :api_client, :endpoint, :url

    def api_client(api_name)
      @apis ||= {}
      raise ArgumentError.new('API name already exists.') if @apis.has_key?(api_name)
      @api_client = api_name
      @apis[@api_client] = {}
      yield(self) if block_given?
    end

    def fetch_client(api_name)
      @apis[api_name]
    end

    def endpoint(endpoint_name)
      raise ArgumentError.new("Endpoint #{endpoint_name} already exists for #{@api_client} API client.") if fetch_client(@api_client).has_key?(endpoint_name)
      @endpoint = endpoint_name
      @apis[@api_client][@endpoint] = {}
      yield(self) if block_given?
    end

    def url=(endpoint_url) 
      fetch_client(@api_client)[@endpoint]['url'] = endpoint_url
    end

  end
end

所以我有这样的测试

  context 'errors' do

    it 'raises an ArgumentError when trying to create an already existent API client' do
      expect {
        obj = MixinTester.new
        obj.api_client('google')
        obj.api_client('google')
      }.to raise_error(ArgumentError,'API name already exists.')
    end

    it 'raises an ArgumentError when trying to create a repeated endpoint for the same API client' do
      expect {
        obj = MixinTester.new
        obj.api_client('google') do |apic|
          apic.endpoint('test1')
          apic.endpoint('test1')
        end
      }.to raise_error(ArgumentError,"Endpoint test1 already exists for google API client.")
    end 

  end

我宁愿将#api_client写成赋值 block

def api_client=(api_name)

这样我就可以写

obj = MixinTester.new
obj.api_client = 'google' do |apic|   # <=== Notice the difference here
  apic.endpoint('test1')
  apic.endpoint('test1')
end

因为我觉得这个notation(with assignment)更有意义。但是，当我以这种方式运行测试时，我只是收到一条错误消息，指出 keyworkd_do 在这种情况下是意外的。

在我看来，赋值 block 的定义是语法糖，不会考虑 block 。

这是正确的吗？有人知道这方面的信息吗？

顺便说一句:MixinTester只是一个用于测试的类，在我的spec/spec_helper.rb中定义为

class MixinTester
  include EDAApiBuilder::Client
end

Answer 1

语法错误

It seems to me that the definition of an assignment [method] is syntactic sugar which won't contemplate blocks.

看来你是对的。看起来没有带有 = 的方法可以接受一个 block ，即使是正常的方法调用并且没有语法糖:

class MixinTester
  def name=(name,&block)
  end

  def set_name(name, &block)
  end
end

obj = MixinTester.new

obj.set_name('test') do |x|
  puts x
end

obj.name=('test') do |x| # <- syntax error, unexpected keyword_do, expecting end-of-input
  puts x
end

备选

哈希参数

另一种方法可以用哈希来写:

class MixinTester
  def api(params, &block)
    block.call(params)
  end
end

obj = MixinTester.new

obj.api client: 'google' do |apic|
  puts apic
end
#=> {:client=>"google"}

您可以根据口味调整方法名称和哈希参数。

带 block 的参数

如果 block 属于方法参数，而不是 setter 方法，则接受语法:

def google(&block)
  puts "Instantiate Google API"
  block.call("custom apic object")
end

class MixinTester
  attr_writer :api_client
end

obj = MixinTester.new

obj.api_client = google do |apic|
  puts apic
end

# =>
# Instantiate Google API
# custom apic object

它看起来很奇怪，但它非常接近您想要实现的目标。