iterating over nested hash ruby-CodePudding

  people = {
    "fruits" => {
        kiwi: ["john","james","diana"],
        apple: ["hibaq","nura","nadia"],
        strawberry: ["hana", "valerie","india"]  },
    "sports" => {
        rugby: ["john","james","diana"],
        football: ["hibaq","nura","nadia"],
        tennis: ["hana", "valerie","india"]
    }
  }

puts 'Enter what category to search'
category = gets.chomp
puts 'Enter what value to search for'
value = gets.chomp

people.select { |person| person[category] == value }
.each { |person| puts person["name"] }

Hi, I am new to ruby and trying to understand hashes a bit more. I want to ask the user for a category e.g "fruits" and then print the array of names that like the fruit. I am unsure how to iterate through the nested hash to access the information. Any guidance would be greatly appreciated. Thank you

CodePudding user response：

The following should work for you.

Please note that I changed the nested hash structure to use Strings instead of Symbols in the inner hashes. Because gets returns already a string that makes it easier to get the data by the key (string) that the user entered.

people = {
  "fruits" => {
    "kiwi" => ["john","james","diana"],
    "apple" => ["hibaq","nura","nadia"],
    "strawberry" => ["hana", "valerie","india"]  
  },
  "sports" => {
    "rugby" => ["john","james","diana"],
    "football" => ["hibaq","nura","nadia"],
    "tennis" => ["hana", "valerie","india"]
  }
}

puts 'Enter what category to search'
category = gets.chomp                   # when entered "sports"
puts 'Enter what value to search for'
value = gets.chomp                      # when entered "rudby"

p people.dig(category, value)
#=> ["john", "james", "diana"]

See Hash#dig. Other options to get data out of a Hash might be Hash#[] or Hash#fetch.

CodePudding user response：

Firstly, you would make life simpler for yourself by using a consistent format when writing your hash people. I suggest

people = {
  fruits: {
    kiwi: ["john","james","diana"],
    apple: ["hibaq","nura","nadia"],
    strawberry: ["hana", "valerie","india"]  },
  sports: {
    rugby: ["john","james","diana"],
    football: ["hibaq","nura","nadia"],
    tennis: ["hana", "valerie","india"]
  }
}

Notice that I have written fruits: { ... rather than 'fruits' => { ... to be consistent with, for example, kiwi: [ ....

With this change we can write the following helper method which can be used for both the outer hash and the inner hashes.

def obtain_response(keys, type) 
  loop do
    puts "Enter what #{type} to search for"
    k = gets.chomp.to_sym
    break k if keys.include?(k)
    puts "There is no such #{type} '#{k}'. Please try again"
  end  
end

We may then write

category = obtain_response(people.keys, 'category')
value =  obtain_response(people[category].keys, 'value')
p people[category][value]

Here is an example session.

category = obtain_response(people.keys, 'category')

Computer                             User
--------                             ----
Enter what category to search for
                                     colours
There is no such category 'colours'. Please try again
Enter what category to search for
                                     sports

Now

category
  #=> :sports

value =  obtain_response(people[category].keys, 'value')

Computer                             User
--------                             ----
Enter what value to search for
                                     darts
There is no such value 'darts'. Please try again
Enter what value to search for
                                     football

Now

value
  #=> :football

We may now display the desired array.

p people[category][value]
  #=> ["hibaq", "nura", "nadia"]

One may of course employ more elaborate prompts, such as

Enter the category to search for ("fruits" or "sports")