dup和clone都返回不同的对象，但修改它们会改变原始对象 [英] Both dup and clone return different objects, but modifying them alters the original object

问题描述

我有一个值数组，当我打印哈希值时，我用作订单的引用。我想修改数组，使数组值漂亮。我想我只是复制或克隆数组，更改值，原始对象将保持未被加载。但是（在irb）...

I have an array of values that I use as a reference for order when I'm printing out hash values. I'd like to modify the array so that the array values are "prettier". I figured I'd just dup or clone the array, change the values and the original object would remain unchanaged. However (in irb)...

@arr = ['stuff', 'things']
a = @arr.clone
b = @arr.dup

所以，至少，a和@arr是不同的对象：

So, at the very least, a and @arr are different objects:

a.object_id == @arr.object_id
=> false

但现在变得奇怪了

a[0].capitalize!
a
=> ['Stuff', 'things']
@arr
=> ['Stuff', 'things'] ##<-what?
b
=> ['Stuff', 'things']## <-what???

ok ...所以修改一个改变别人，让它改回来？

ok... so modifying one changes the others, lets change it back?

a[0] = 'stuff'
a
=> ['stuff', 'things']
@arr
=> ['Stuff', 'things'] ## <- WHAT?????

为了完整性b [1] .capitalize！具有相同的效果，利用所有三个阵列的第二个位置

For completeness b[1].capitalize! has the same effect, capitalizing all three array's second position

所以...大写结束时的爆炸是否使其变得更有效力？足够交叉到其他对象？我知道这样做的其他方法，但这对我来说似乎非常奇怪。我认为这与浅拷贝有关。关于最佳方法的建议？

So... does the bang on the end of capitalize make it extra potent? Enough to cross over to other objects?? I know of other ways of doing this, but this just seemed extremely odd to me. I assume this has something to do with being a "shallow copy". Suggestions on the best way to do this?

推荐答案

dup code>克隆创建数组的新实例，但不是内容，它不是深层次的副本。

dupand clone make new instances of the arrays, but not of the content, it is no deep copy.

请参阅： / p>

See:

array0 = ['stuff', 'things']
array1 = array0.clone
array2 = array0.dup

puts "Array-Ids"
p array0.object_id
p array1.object_id
p array2.object_id

puts "Object ids"
array0.each_with_index{|_,i|
  p array0[i].object_id
  p array1[i].object_id
  p array2[i].object_id
  p '--------'
}

数组中的元素共享相同的object_id - 它们是相同的对象。数组有不同的对象ids。

The elements inside the array share the same object_id - they are the same object. The arrays have different object ids.

当你 a [0] .capitalize！你修改一个对象，

When you a[0].capitalize! you modify an object, which is part in three different arrays.

另请参见

• 重复Ruby数组的字符串


• 在Ruby中复制数组


• 如何在Ruby中创建对象的深层副本？

• Duplicating a Ruby array of strings
• Deep copy of arrays in Ruby
• How to create a deep copy of an object in Ruby?

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