为什么我不能修改的方法数组的值？

问题描述

在下面的code片段，数组甲板应该等于 [6,9,5,6,5,1,2 ] ，因为红宝石按引用传递数组。方法调用后，甲板上的值不会改变。这是为什么？

In the code fragment below, the array deck should equal [6,9,5,6,5,1,2] since Ruby passes arrays by reference. After the method call, the values of deck does not change. Why is that?

def count_cut!(deck)
  s1, s2 = deck[0, deck.last], deck[deck.last..-2]
  deck = s2 + s1 + [deck.last]
end

deck = [5, 1, 6, 9, 5, 6, 2]
count_cut!(deck)
p deck

我使用Ruby 1.9.2-P180。

I am using Ruby 1.9.2-p180.

推荐答案

分配到甲板不变异中传递数组中。这是像对待一个局部变量在函数定义的范围。您可以拨打 deck.replace 如果你真的想变异它。

Assigning to deck does not mutate the array that was passed in. It is treated like a local variable in the scope of the function definition. You can call deck.replace if you really want to mutate it.

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