通过基于该项目的属性分组的对象的阵列构建哈希 [英] Building Hash by grouping array of objects based on a property of the items

问题描述

我想知道，如果在Ruby 1.9的做到这一点更规范的方法

我有一大堆对象的数组，我使用阵列中的每个对象的属性要它们分成一个Hash。

非常简单的例子：

 ＆GT; SH = {}
 = GT; {}
＆GT; AERS =％W（A B C D AB BC德ABC）
 = GT; [A，B，C，D，AB，BC，德，ABC]
＆GT; aers.each做| AER |
＆GT; SH [aer.size] = []如果SH [aer.size] .nil？
＆GT; SH [aer.size＆LT;＆LT; AER
＆GT;结束
= GT; [A，B，C，D，AB，BC，德，ABC]
＆GT; SH
 = GT; {1 =＆GT;A，B，C，D]，2 =＆GT;AB，BC，德]，3 =＆GT;ABC] }
 

我想这一点，但它的输出是错误的（因为你可以看到）：

  SH = Hash.new（[]）
 = GT; {}
＆GT; aers.each做| AER |
＆GT; SH [aer.size＆LT;＆LT; AER
＆GT;结束
 = GT; [A，B，C，D，AB，BC，德，ABC]
＆GT; SH
 = GT; {}
 

解决方案

红宝石一直期待您的需要，并已经得到了你覆盖着<一个href=\"http://ruby-doc.org/core/classes/Enumerable.html#M001497\"><$c$c>Enumerable#group_by:

  IRB（主）：001：0＆GT; AERS =％W（A B C D AB BC德ABC）
＃=＆GT; [A，B，C，D，AB，BC，德，ABC]IRB（主）：002：0＆GT; aers.group_by {| S | s.size}
＃=＆GT; {1 =＆GT;A，B，C，D]，2 =＆GT;AB，BC，德]，3 =＆GT;ABC] }
 

在Ruby 1.9的，你可以使这个甚至更短：

  IRB（主）：003：0＆GT; aers.group_by（安培;：大小）
＃=＆GT; {1 =＆GT;A，B，C，D]，2 =＆GT;AB，BC，德]，3 =＆GT;ABC] }
 

I'm wondering if there is a more canonical way to do this in ruby 1.9

I have an array with a bunch of objects and I want to group them into a Hash using a property of each object in the array.

Very simplified example:

> sh = {}
 => {} 
> aers = %w(a b c d ab bc de abc)
 => ["a", "b", "c", "d", "ab", "bc", "de", "abc"] 
> aers.each do |aer|
>     sh[aer.size] = [] if sh[aer.size].nil?
>     sh[aer.size] << aer
>   end
=> ["a", "b", "c", "d", "ab", "bc", "de", "abc"] 
> sh
 => {1=>["a", "b", "c", "d"], 2=>["ab", "bc", "de"], 3=>["abc"]} 

I tried this, but its output is wrong (as you can see):

 sh = Hash.new([])
 => {} 
> aers.each do |aer|
>     sh[aer.size] << aer
>   end
 => ["a", "b", "c", "d", "ab", "bc", "de", "abc"] 
> sh
 => {} 

解决方案

Ruby has anticipated your need, and has got you covered with Enumerable#group_by:

irb(main):001:0> aers = %w(a b c d ab bc de abc)
#=> ["a", "b", "c", "d", "ab", "bc", "de", "abc"]

irb(main):002:0> aers.group_by{ |s| s.size }
#=> {1=>["a", "b", "c", "d"], 2=>["ab", "bc", "de"], 3=>["abc"]}

In Ruby 1.9, you can make this even shorter with:

irb(main):003:0> aers.group_by(&:size)
#=> {1=>["a", "b", "c", "d"], 2=>["ab", "bc", "de"], 3=>["abc"]}

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