通过键

Question

的阵列组红宝石哈希元素值是我得到：

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

散列结构和设置键可以变化的。
我需要得到

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

谢谢！

Answer 1

您可以使用inject遍历您的嵌套结构：

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

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

所以，你只需要修改该做的最后关键一组。也许类似于

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的类似，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