Tracing a nested Ruby Hash with an array of keys

Question

Given a hash with n levels of nested values, the field name and path

contact = {
  "Email" => "[e-mail]",
  "Account" => {
    "Exchange" => true,
    "Gmail" => false,
    "Team" => {
      "Closing_Sales" => "Bob Troy",
      "Record" => 1234
    }
  }
}

field = "Record"
path = ["Account", "Team"] #Must support arbitrary path length

How to determine the method that will retrieve the value of the field at the end of the path.

def get_value(hash, field, path)
  ?
end

get_value(contact, "Record", ["Account", "Team"])
=> 1234

Answer 1

Consider the "field" as the last element of the "path". Then just

def grab_it(h, path)
  h.dig(*path)
end

grab_it contact, ["Account", "Team", "Record"]
  #=> 1234 
grab_it contact, ["Account", "Team", "Rabbit"]
  #=> nil
grab_it(contact, ["Account", "Team"]
  # => {"Closing_Sales"=>"Bob Troy", "Record"=>1234} 
grab_it contact, ["Account"]
  #=> {"Exchange"=>true, "Gmail"=>false, "Team"=>{"Closing_Sales"=>"Bob Troy",
  #    "Record"=>1234}} 

Hash # dig added in v2.3.

Answer 2

You can use Array#inject: to indicate hash['Account']['Team'], then return_value_of_inject['Record']:

def get_value(hash, field, path)
  path.inject(hash) { |hash, x| hash[x] }[field]
end

get_value(contact, field, path) # => 1234

By the way, what about get_value(contact, ['Account', 'Team', 'Record'])?

def get_value2(hash, path)
  path.inject(hash) { |hash, x| hash[x] }
end

get_value2(contact, ['Account', 'Team', 'Record']) # => 1234

or get_value(contact, 'Account.Team.Record')

def get_value3(hash, path)
  path.split('.').inject(hash) { |hash, x| hash[x] }
end

get_value3(contact, 'Account.Team.Record')   # => 1234

Answer 3

def get_value(contact, field, path)
  path.inject(contact) {|p, j| p.fetch(j, {}) }.fetch(field, nil)
end