How to append ID key:value pairs when iterating over an array of hashes in Ruby?-CodePudding

I have an array of hashes, e.g.:

{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown"}
{"Breed"=>"Pug", "Size"=>"Small", "Colour"=nil}
{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown"}
{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"=nil}

I want to give them all ID values based on a given search criteria. For example, searching by Size should return:

{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="0"}
{"Breed"=>"Pug", "Size"=>"Small", "Colour"=nil, "ID"="1"}
{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="0"}
{"Breed"=>"Poodle", "Size"=>"Medium", "Colour"=nil, "ID"="0"}

I have written the following code which checks each hash in the sequence with the following hashes.

for i in 0..data.length-2
  data[i].store("ID", i)

  for j in i 1..data.length-1
    output = (data[i].keys & data[j].keys).select { |k| data[i][k] == data[j][k] }

    if output.include? searchTerm
      puts "Match!"
      puts "---"
      data[j].store("ID", data[i]["ID"])
    else
      puts "No match :("
      puts "---"
    end
  end

  puts "---Finished checking row---"    
end

puts data

The issue is twofold:

A. Nil values count as a match, e.g when searching by Colour:

{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="0"}
{"Breed"=>"Pug", "Size"=>"Small", "Colour"=nil, "ID"="1"}
{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="0"}
{"Breed"=>"Poodle", "Size"=>"Medium", "Colour"=nil, "ID"="1"}

B. Matches seem to only work for the last pair found, e.g. when searching by Size:

{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="0"}
{"Breed"=>"Pug", "Size"=>"Small", "Colour"=nil, "ID"="1"}
{"Breed"=>"Beagle", "Size"=>"Medium", "Colour"="Brown", "ID"="2"}
{"Breed"=>"Poodle", "Size"=>"Medium", "Colour"="White", "ID"="2"}

In summary, I want to ignore nil values so they don't count as matches and for all instances of the same key:value pair to have the same value for the ID key.

CodePudding user response：

Don't use for loops for array iteration. Ruby has plenty of nice methods for doing that.

Here is my solution:

hashes = [{"Breed" => "Beagle", "Size" => "Medium", "Colour" => "Brown"},
          {"Breed" => "Pug", "Size" => "Small", "Colour" => nil},
          {"Breed" => "Beagle", "Size" => "Medium", "Colour" => "Brown"},
          {"Breed" => "Beagle", "Size" => "Large", "Colour" => nil}]

def search_id(elements, search_key)
  # Get rid of elements with nil values.
  target_elements = elements.reject {|e| e[search_key].nil?}

  resul = []
  id = 0

  # Iterate through target_elements
  target_elements.each do |currentElement|

    # Check if exsits an element with the same value in the resul array
    match = resul.find {|previousElement| currentElement[search_key] == previousElement[search_key]}

    if match
      # Use previous id
      currentElement[:id] = match[:id]
    else
      # Assing a new id
      currentElement[:id] = id
      id  = 1
    end

    # Add element to result
    resul << currentElement
  end

  resul
end

puts search_id(hashes, 'Size')

CodePudding user response：

I think that it might be worth considering grabbing all of the unique values from the searched entries first and then assigning each of them an id inside a hash (with the available terms as the keys), so that you can simply loop though the hashes and grab the correct id from the pre-generated hash. e.g. something like:

hashes = [
    {"Breed"=>"Beagle", "Size"=>"Medium", "Colour"=>"Brown"},
    {"Breed"=>"Pug", "Size"=>"Small", "Colour"=>nil},
    {"Breed"=>"Beagle", "Size"=>"Medium", "Colour"=>"Brown"},
    {"Breed"=>"Beagle", "Size"=>"Medium", "Colour"=>nil}
]


def append_id(items, search_key)
    id_map = items.
        map { |hash| hash[search_key] }.
        uniq.
        reject { |value| value.nil? }.
        map.with_index { |value, index| [value, index] }.
        to_h
    
    items.each do |hash|
        value = hash[search_key]
        hash['ID'] = id_map[value] unless value.nil?
    end
    
    items
end

append_id(hashes, 'Size')