在 Ruby 中，为什么 Array.new(size, object) 创建一个包含对同一对象的多个引用的数组? [英] In Ruby, why does Array.new(size, object) create an array consisting of multiple references to the same object?

问题描述

如这个答案中所述，Array.new(size, object) 创建一个数组，其中 size 引用相同的 object.

As mentioned in this answer, Array.new(size, object) creates an array with size references to the same object.

hash = Hash.new
a = Array.new(2, hash)
a[0]['cat'] = 'feline'
a # => [{"cat"=>"feline"},{"cat"=>"feline"}]
a[1]['cat'] = 'Felix'
a # => [{"cat"=>"Felix"},{"cat"=>"Felix"}]

为什么 Ruby 会这样做，而不是对 object 进行 dup 或 clone?

Why does Ruby do this, rather than doing a dup or clone of object?

推荐答案

因为这就是 文档 说确实如此.注意 Hash.new 只被调用一次，所以当然只有一个 Hash

Because that's what the documentation says it does. Note that Hash.new is only being called once, so of course there's only one Hash

如果要为数组中的每个元素创建一个新对象，请将一个块传递给 Array.new 方法，该块将为每个新元素调用:

If you want to create a new object for every element in the array, pass a block to the Array.new method, and that block will be called for each new element:

>> a = Array.new(2) { Hash.new }
=> [{}, {}]
>> a[0]['cat'] = 'feline'
=> "feline"
>> a
=> [{"cat"=>"feline"}, {}]
>> a[1]['cat'] = 'Felix'
=> "Felix"
>> a
=> [{"cat"=>"feline"}, {"cat"=>"Felix"}]

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