A better way of creating a ruby hash?

Question

I want to build a hash from an array of rows from a DB. I can easily do it with the code below. I've come to Ruby from PHP and this is how I would do it. Is there a better/proper way to do this in Ruby (or Rails)?

def features_hash
  features_hash = {}
  product_features.each do |feature|
    features_hash[feature.feature_id] = feature.value
  end

  features_hash
end

# {1 => 'Blue', 2 => 'Medium', 3 => 'Metal'}

Answer 1

You can use Hash[] :

Hash[ product_features.map{|f| [f.feature_id, f.value]}  ]

Would you like this better?

product_features.map{|f| [f.feature_id, f.value]}.to_h # no available (yet?)

Then go and check out this feature request and comment on it!

Alternative solutions:

product_features.each_with_object({}){|f, h| h[f.feature_id] = f.value}

There is also group_by and index_by which could be helpful, but the values will be the features themselves, not their value .

Answer 2

You can use index_by for this:

product_features.index_by(&:id)

This produces the same results as hand-constructing a hash with id as the key and the records as the values.

Answer 3

Your code is a good way to do it. Another way is:

def features_hash
  product_features.inject({}) do |features_hash, feature|
    features_hash[feature.feature_id] = feature.value
    features_hash
  end
end