Ruby(Hard Way, Ex48) matching array to hash then assigning values to struct?

Question

I've looked at everything from the Ruby docs on struct, map, array & hash; but for whatever reason haven't grasped HOW to do this. I have two questions.

What's a good way to see if an array and a hash have a value in common?
From a hash, how could I find a value and "automatically" take it's key (or viceversa) and include them in a new instance of something else (e.g. Pair.new)?

I saw this SO response, but it wasn't much help...Learn Ruby Hard Way ex. 48

Also looked at this too, but it didn't work & Zed says to use map func... Using Ruby, what is the most efficient way to check if any key in a hash matches any values within an Array

The exercise instructions can be found here. Ruby The Hard Way EX.48 Instructions

MY CODE (try#2080)

class Lexicon

Pair = Struct.new(:token, :key)

def scan(stuff)
    @words = stuff.split(" ")
    return analyze
end

def analyze

    hash = { :direction => "north", :direction => "south", 
            :direction => "east", :direction => "west", :verb => "go",  
                                 :verb => "stop"}

    @words.map do |word|
        if word == hash[:direction]
        #i need something here that says if word matches a value in hash... 
        #assign matching key/value to a new instance of Pair
            Pair.new(word)
        else
                            *#puts to see if anything is sticking* 
            puts "Oh god its not working #{word}"
            puts Pair[]
            puts hash[:direction]
           end
       end
  end
end

a = Lexicon.new()
a.scan("north mama jeffrey homie")

TERMINAL

$ ruby lexicon.rb
Oh god its not working north
#<struct Lexicon::Pair token=nil, key=nil>
west

Oh god its not working mama
#<struct Lexicon::Pair token=nil, key=nil>
west

Oh god its not working Jeffrey
#<struct Lexicon::Pair token=nil, key=nil>
west

Oh god its not working homie
#<struct Lexicon::Pair token=nil, key=nil>
west

MY CODE #2081 Same as above but,

   hash.each do |k, v|
      if v == @words
      #i need something here that says if word matches a value in hash... 
      #assign matching key/value to a new instance of Pair
        Pair.new(k,v)
      else
        puts "Oh god its not working"
        puts Pair[]
        puts hash[:direction]
        puts @words
      end
   end

TERMINAL

Oh god its not working
#<struct Lexicon::Pair token=nil, key=nil>
...
...

For your definition of hash, irb will say: hash => {:direction=>"west", :verb=>"stop"}. Do you see why? — Cary Swoveland
– Cary Swoveland, Commented Nov 16, 2013 at 22:59

elreimundo · Accepted Answer · 2013-11-16 23:13:31Z

2

You've got several issues here. Most importantly, your hash is not functional; hashes are built on key-value pairs with unique keys, so your hash is actually the same as the following:

hash = { :direction => "west", :verb => "stop"}

You would probably be better off swapping the key-value pairs in your hash as follows:

hash = { "north" => :direction, "south" => :direction, 
        "east" => :direction, "west" => :direction, "go" => :verb,  
                             "stop" => :verb }

@words.map do |word|
  hash.keys.include?(word) ? Pair.new(hash[word], word) : Pair.new(:error, word)
end

edited Nov 16, 2013 at 23:13

answered Nov 16, 2013 at 23:02

elreimundo

6,2961 gold badge16 silver badges6 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jay Bobo Over a year ago

thanks @elreimundo! is there an elegant way I could accomplish the same without swapping the key-value pairs?

johnsyweb Over a year ago

Why hash.keys.include?(word) rather than hash.key?(word)?

Amit Kumar Gupta · Accepted Answer · 2013-11-16 23:02:41Z

0

def have_common_value?(array, hash)
  hash.values.any? { |v| array.include? v }
end

def get_pair_from_value(hash, value)
  hash.find { |k,v| v == value }
end

answered Nov 16, 2013 at 23:02

Amit Kumar Gupta

18.8k9 gold badges52 silver badges67 bronze badges

1 Comment

Jay Bobo Over a year ago

Thanks @Amit I'm going to try these too.

CDub · Accepted Answer · 2013-11-16 23:02:57Z

0

A hash can only have one unique key per value, therefore, part of your problem is that the hash you generate above will only return one :direction and one :location.

This should help get you closer to what you're looking for:

class Lexicon

  Pair = Struct.new(:token, :key)

  def scan(stuff)
    @words = stuff.split(" ")
    return analyze
  end

  def analyze
    hash = { :directions => { :north => "north", :south => "south", :east => "east", :west => "west" },
             :actions => { :verb => "go", :verb => "stop" } }

    @words.map do |word|
      if hash[:directions].values.include?(word)
        Pair.new(word)
      else
        puts "Oh god its not working #{word}"
        puts Pair[]
        puts hash[:directions]
      end
    end
  end
end

a = Lexicon.new()
a.scan("north mama jeffrey homie")

answered Nov 16, 2013 at 23:02

CDub

13.4k4 gold badges53 silver badges71 bronze badges

1 Comment

Jay Bobo Over a year ago

Thanks @CDub but I'd need to incorporate :directions for each matching value and pass that to Pair (e.g Pair.new (:directions,'north'))

Collectives™ on Stack Overflow

Ruby(Hard Way, Ex48) matching array to hash then assigning values to struct?

MY CODE (try#2080)

TERMINAL

MY CODE #2081 Same as above but,

TERMINAL

3 Answers 3

2 Comments

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

MY CODE (try#2080)

TERMINAL

MY CODE #2081 Same as above but,

TERMINAL

3 Answers 3

2 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related