在Rails中的ruby中提取哈希数据

Question

I'm working with sabre api ( test licence ) in my rails application, i get a JSON response and when I parse it a get this hash

{
    "OriginLocation"=>"DEN",
    "Destinations"=>[
    {
    "Rank"=>1,
    "Destination"=>{
    "DestinationLocation"=>"LAX",
    "AirportName"=>"Los Angeles International Airport",
    "CityName"=>"Los Angeles",
    "CountryCode"=>"US",
    "CountryName"=>"United States",
    "RegionName"=>"North America",
    "Type"=>"Airport"
    }
    },
    {
    "Rank"=>2,
    "Destination"=>{
    "DestinationLocation"=>"LAS",
    "AirportName"=>"McCarran International Airport",
    "CityName"=>"Las Vegas",
    "CountryCode"=>"US",
    "CountryName"=>"United States",
    "RegionName"=>"North America",
    "Type"=>"Airport"
    }
    },
    {
    "Rank"=>3,
    "Destination"=>{
    "DestinationLocation"=>"CHI",
    "CountryCode"=>"US",
    "CountryName"=>"United States",
    "RegionName"=>"North America",
    "MetropolitanAreaName"=>"Chicago",
    "Links"=>[
    {
    "rel"=>"airportsInCity",
    "href"=>"https://api.test.sabre.com/v1/lists/supported/cities/CHI/airports"
    }
    ],
    "Type"=>"City"
    }
    } 
    ...
    }

How can i extract the data (ex: destination) information from it? I tried this code but i get an error " undefined method ``each' for nil:NilClass "

@hash['Destinations'].each do |key, value|
  puts key
  value.each do |k,v|
    puts k
    puts v
  end
end

Answer 1

Even though you've specified key and value , only key is populated (with the entire hash data), and value is nil . That's why you're getting an error.

Assuming you're on Ruby 2.3 or above, I suggest you use something like this instead:

@hash['Destinations'].map { |d| d.dig('Destination', 'CityName') }
#=> ["Los Angeles", "Las Vegas", nil]

You can read up more on dig here. It's useful for this kind of deeply nested data, and will protect you from keys that don't exist (and return nil instead); as long as you don't mix its usage on arrays and hashes.