I have an hash like below:
hash = {"a": [{"c": "d", "e": "f"}] }
Normally we can access it like hash["a"][0]["c"].
But, I have a string like:
string = "a[0]['c']"
(This can change depending upon user input)
Is there any easy way to access hash using above string values?
Assuming that the user inputs numbers for array indices and words for hash keys:
keys = string.scan(/(\d+)|(\w+)/).map do |number, string|
number&.to_i || string.to_sym
end
hash.dig(*keys) # => "d"
Indexible module, where you have to implement #[] and it gives you other goodies like #dig.
dig will "dig" into any object that responds to dig—indeed it will! eval.in/691998 That's handy.Indexible module in the future. (:
You could do this :
hash = { 'a' => [{ 'c' => 'd', 'e' => 'f' }] }
string = "a[0]['c']"
def nested_access(object, string)
string.scan(/\w+/).inject(object) do |hash_or_array, i|
case hash_or_array
when Array then hash_or_array[i.to_i]
when Hash then hash_or_array[i] || hash_or_array[i.to_sym]
end
end
end
puts nested_access(hash, string) # => "d"
The input string is scanned for letters, underscores and digits. Everything else is ignored :
puts nested_access(hash, "a/0/c") #=> "d"
puts nested_access(hash, "a 0 c") #=> "d"
puts nested_access(hash, "a;0;c") #=> "d"
An incorrect access value will return nil.
It also works with symbol as keys :
hash = {a: [{c: "d", e: "f"}]}
puts nested_access(hash, "['a'][0]['c']")
It brings the advantage of being not too strict about user input, but it does have the drawback of not recognizing keys with spaces.
{ "Hash keys aren't so \"predictable\"" => 1 }{"a": 1} == {a: 1} == {:a => 1}. There's not really a good solution here if arbitrary hash keys are allowed. P.S. \w includes _, so [\w_] is redundant.you can use gsub to clean other characters into an array and use that array to access your hash
hash = {"a": [{"c": "d", "e": "f"}] }
string = "a[0]['c']"
tmp = string.gsub(/[\[\]\']/, '').split('')
#=> ["a", "0", "c"]
hash[tmp[0].to_sym][tmp[1].to_i][tmp[2].to_sym]
#=> "d"
a-zA-Z0-9_?