need help in getting nested ruby hash hierarchy

Question

I have hash deep nested hash and i want the hierarchy(parent to child) for each key as an array.

for example -

 hash = {
"properties"=>{
    "one"=>"extra",
    "headers"=>{
        "type"=>"object",
        "type1"=>"object2"
    },
    "entity"=>{
        "type"=>"entype"
    },       
},
"sec_prop"=>"hmmm"
}

for this hash I want output as given below, as a separate array for each key.

[properties,one]
[properties,headers,type]
[properties,headers,type1]
[properties,entity,type]
[sec_prop]

i have been trying and searching this for so long through some recursive methods but it doesn't seems to work for me any help will be appreciated.

important thing to notice here is there are duplicate keys in the same hash as a nesting for example type key is repeated in both headers and entity. so that i need proper hierarchy to identify the proper key

and i should get this array of hierarchy only for those keys whose value is not a another hash.

It should be in the format above given but any other solutions also welcome

thanks.!

-1 and close vote because the logic for [properties,sec_prop] is not clear. — sawa
– sawa, Commented Mar 11, 2014 at 17:36
I suspect an error in either the input or the output data: sec_prop is not nested under properties in the input data, but it is in the output data. — Wayne Conrad
– Wayne Conrad, Commented Mar 11, 2014 at 17:39
You say you've been trying, but you don't show us any code. It's easier for us to fix your attempt than it is to write something unrelated to your code and you shoehorn it in. — the Tin Man
– the Tin Man, Commented Mar 11, 2014 at 17:48

Wayne Conrad · Accepted Answer · 2014-03-11 17:45:51Z

5

Recursion to the rescue:

def hashkeys(o, keys = [], result = [])
  if o.is_a?(Hash)
    o.each do |key, value|
      hashkeys(value, keys + [key], result)
    end
  else
    result << keys
  end
  result
end

This is a depth first search which accumulates keys until it gets to a leaf (a non-Hash value). Each time it get to a leaf, it adds the accumulated keys to the result.

pp hashkeys(hash)
# => [["properties", "one"],
# =>  ["properties", "headers", "type"],
# =>  ["properties", "headers", "type1"],
# =>  ["properties", "entity", "type"],
# =>  ["sec_prop"]]

edited Mar 11, 2014 at 17:45

answered Mar 11, 2014 at 17:39

Wayne Conrad

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5 Comments

Arup Rakshit Over a year ago

I don't know, how you code it.. I am still connectionless. :(

Wayne Conrad Over a year ago

@Arup, I'll improve the answer, if I can. Is there any one thing that confuses you the most?

Arup Rakshit Over a year ago

No.. Your code is perfect.. I was not able to understand what OP's logic is. This part [properties,sec_prop].

Wayne Conrad Over a year ago

@Arup, Oh, that. Yes. I decided it must be a mistake in his question. The incorrect indentation of the input hash would make such a mistake easier.

Kirti Thorat Over a year ago

@WayneConrad +1 You have written the code as succinct as it can get.

Arup Rakshit · Accepted Answer · 2014-03-11 21:30:16Z

1

Here is my try :

hash = {
  "properties"=>{
    "one"=>"extra",
    "headers"=>{
      "type"=>"object",
      "type1"=>"object2"
    },
    "entity"=>{
      "type"=>"entype"
    },       
  },
  "sec_prop"=>"hmmm"
}

def fetch_keys(h)
  h.flat_map do |k,v|
    if v.is_a?(Hash)
      fetch_keys(v).map do |keys|
        [k] + Array(keys)
      end
    else
      k
    end
  end
end

fetch_keys(hash)
# => [["properties", "one"],
#     ["properties", "headers", "type"],
#     ["properties", "headers", "type1"],
#     ["properties", "entity", "type"],
#     "sec_prop"]

edited Mar 11, 2014 at 21:30

answered Mar 11, 2014 at 21:25

Arup Rakshit

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1 Comment

Arup Rakshit Over a year ago

Note: I think it can be re-factored to some extent. So welcome all viewer advice on this..

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