如何在 ruby​​/rails 中合并两个列表并删除重复项? [英] How do I merge two lists, and remove duplicates, in ruby/rails?

问题描述

我有一个源对象

class Source

def ==(other)
  return false if self.url == nil || other == nil
  self.url == other.url
end

我有以下几点:

def self.merge_internal_and_external_sources(sources=[], external_sources=[])
    (sources + external_sources).uniq
end

我想合并这两个列表，并开始从 external_sources 中剔除源列表中已经存在的项目.我不知道如何雄辩地做到这一点?

I would like to merge the two lists, and start kicking out items from external_sources if they already exist in sources list. I am not sure how to do this eloquently?

我也试过:

sources | external_sources

但这产生的结果没有删除重复项，因为我的 == 比较想要在内部比较 'url' 属性?例如:

but this yields a result without the duplicates being removed because of my == comparison want to compare the 'url' attribute internally? For example:

[src1] == [src2] # true
list = [src1] | [src2] 
list.size # 2

推荐答案

我不知道你说的合并"是什么意思(数组没有 #merge 方法，只有散列)，但您可以像这样简化代码:

I am not sure what do you mean by "merge" (there is no #merge method on arrays, only on hashes), but you can simplify your code like this:

merged = sources | external_sources

要使其与您的类一起工作，您还需要两个方法:#hash(实例哈希值，用于初步相等性筛选)和 #eql?，用于确认相等:

To make it work with your class, you need two more methods: #hash (instance hash value, used for preliminary equality screening), and #eql?, used to confirm equality:

class Source
  def hash
    url.hash + 1
  end
  # Or delegate it to the url:
  # require 'active_support/core_ext/module/delegation'
  # delegate :hash, to: :url

  def eql? other
    return false if url.nil? || other.url.nil?
    url == other.url
  end
end

#hash 和 #eql? 是每个类都应该具备的基本工具.添加这些之后，#| 和 #& 方法将开始在 Source 实例的数组上运行.

#hash and #eql? are among the basic facilities every class should have. After adding these, #| and #& methods will start to behave on arrays of Source instances.

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