在循环中更改数组中的条目

Question

arr = ["red","green","blue","yellow"]

arr.each do |colour|
  if colour == "red"
    colour = "green"
  end
end

puts arr.inspect

以上代码输出:

["red", "green", "blue", "yellow"]

但为什么不呢？

["green", "green", "blue", "yellow"]

我认为颜色是对数组中当前元素的引用,无论我做了什么都会影响该数组元素？

Answer 1

当您在arr.each块内时,colour变量将绑定到arr数组中的一个对象.

但是,只要colour = "green"在块中进行赋值,现在colour变量就绑定到一个新对象(即一个值为的String "green"),原始文件arr保持不受影响.

实现您所谈论的内容的一种方法是:

arr.each_index do |i|
  arr[i] = "green" if arr[i] == "red"
end

它直接操纵数组.