通过键数组设置ruby哈希元素值

Question

这是我得到的：

hash = {:a => {:b => [{:c => old_val}]}}
keys = [:a, :b, 0, :c]
new_val = 10

哈希结构和密钥集可以变化。
我需要得到

hash[:a][:b][0][:c] == new_val

谢谢！

Answer 1

您可以使用inject来遍历嵌套结构：

hash = {:a => {:b => [{:c => "foo"}]}}
keys = [:a, :b, 0, :c]

keys.inject(hash) {|structure, key| structure[key]}
# => "foo"

所以，你只需要修改它就可以在最后一个键上进行设置。 也许是这样的

last_key = keys.pop
# => :c

nested_hash = keys.inject(hash) {|structure, key| structure[key]}
# => {:c => "foo"}

nested_hash[last_key] = "bar"

hash
# => {:a => {:b => [{:c => "bar"}]}}

Answer 2

与Andy相似，但您可以使用Symbol#to_proc来缩短它。

hash = {:a => {:b => [{:c => :old_val}]}}
keys = [:a, :b, 0, :c]
new_val = 10
keys[0...-1].inject(hash, &:fetch)[keys.last] = new_val