从ActiveRecord模型的集合中构建哈希 [英] Build hash from collection of ActiveRecord Models

问题描述

我正在尝试从模型构建哈希。

I'm trying to build a hash from a Model.

这是我要构建的哈希类型。

This is the type of hash I want to build.

{"United Sates" => "us", "United Kingdom" => "uk" .....}

我已经尝试了很多方法，

I have tried so many ways now I'm just going around in circles.

这只是我一些可怜的尝试。

Here are just some of my poor attempts.

select = Array.new
countries.each do |country|
  # select.push({country.name => country.code })
  # select[country.name][country.code]
end

h = {}

countries.each do |c|
  # h[] = {c.name => c.code}
  # h[] ||= {} 
  # h[][:name] = c.name
  # h[][:code] = c.code 
  #h[r.grouping_id][:name] = r.name
  # h[r.grouping_id][:description] = r.description
end

请提供一些建议。

谢谢

推荐答案

以下是一些单线替代方法：

Here are some one-liner alternatives:

# Ruby 2.1+
name_to_code = countries.map{ |c| [c.name,c.code] }.to_h

# Ruby 1.8.7+
name_to_code = Hash[ countries.map{ |c| [c.name,c.code] } ]

# Ruby 1.8.6+
name_to_code = Hash[ *countries.map{ |c| [c.name,c.code] }.flatten ]

# Ruby 1.9+
name_to_code = {}.tap{ |h| countries.each{ |c| h[c.name] = c.code } }

# Ruby 1.9+
name_to_code = countries.to_a.each_with_object({}){ |c,h| h[c.name] = c.code }

@Addicted在下面的评论表示感谢：

Courtesy of @Addicted's comment below:

# Ruby 1.8+
name_to_code = countries.inject({}){ |r,c| r.merge c.name=>c.code }

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