如何通过散列更改数组中的值？

Question

我想通过散列来改变数组的值，例如：

arr = ['g','g','e','z'] 
positions = {1 => arr[0], 2 => arr[1]} 

positions[1] = "ee" 

问题是，改变了一个散列，而不是阵列。当我做p arr它仍然输出['g','g','e','z']。有没有解决的办法？

Answer 1

你将需要添加另一行代码，做你想做什么：

arr = ['g','g','e','z'] 
positions = {1 => arr[0], 2 => arr[1]} 

positions[1] = "ee" 
arr[0] = positions[1] 

另一种选择是，以使该自动更新阵列为你的方法，是这样的：

def update_hash_and_array(hash, array, val, index) 
    # Assume that index is not zero indexed like you have 
    hash[index] = val 
    array[index - 1] = val 
end 

update_hash_and_array(positions, arr, "ee", 1) # Does what you want 

Answer 2

这是可能的代码到您的散列使用特效。

arr = ['g','g','e','z'] 

positions = {1 => -> (val) { arr[0] = val } } 


positions[1].('hello') 
# arr => ['hello', 'g', 'e', 'z'] 

如果您想要生成一个可以修改任何数组的散列，那么您可以概括这一点。

def remap_arr(arr, idx) 
    (idx...arr.length+idx).zip(arr.map.with_index{|_,i| -> (val) {arr[i] = val}}).to_h 
end 

arr = [1,2,3,4,5,6] 
positions = remap_arr(arr, 1) 

positions[2].('hello') 
# arr => [1,'hello',3,4,5,6] 

positions[6].('goodbye') 
# arr => [1,'hello',3,4,5,'goodbye'] 

但我希望这只是一个思想实验，没有理由的方式来改变数组索引行为工作从1而不是0。在这种情况下启动，您通常只是想弥补索引你必须匹配正确的数组索引（从零开始）。如果这还不够，这是一个标志，你需要一个不同的数据结构。

Answer 3

#!/usr/bin/env ruby 

a = %w(q w e) 

h = { 
    1 => a[0] 
} 

puts a[0].object_id # 70114787518660 
puts h[1].object_id # 70114787518660 
puts a[0] === h[1] # true 

# It is a NEW object of a string. Look at their object_ids. 
# That why you can not change value in an array via a hash. 
h[1] = 'Z' 

puts a[0].object_id # 70114787518660 
puts h[1].object_id # 70114574058580 
puts a[0] === h[1] # false 

h[2] = a 

puts a.object_id # 70308472111520 
puts h[2].object_id # 70308472111520 
puts h[2] === a  # true 

puts a[0] === h[2][0] # true 
# Here we can change value in the array via the hash. 
# Why? 
# Because 'h[2]' and 'a' are associated with the same object '%w(q w e)'. 
# We will change the VALUE without creating a new object. 
h[2][0] = 'X' 

puts a[0]    # X 
puts h[2][0]   # X 
puts a[0] === h[2][0] # true