Convert an array to hash, where keys are the indices - ruby

Question

I am transforming an array into a hash, where the keys are the indices and values are the elements at that index.
Here is how I have done it
# initial stuff
arr = ["one", "two", "three", "four", "five"]
x = {}
# iterate and build hash as needed
arr.each_with_index {|v, i| x[i] = v}
# result
>>> {0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}
Is there a better (in any sense of the word "better") way to do it?

Answer 1

arr = ["one", "two", "three", "four", "five"]
x = Hash[(0...arr.size).zip arr]
# => {0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}

Answer 2

Ruby < 2.1:
Hash[arr.map.with_index { |x, i| [i, x] }]
#=> {0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}
Ruby >= 2.1:
arr.map.with_index { |x, i| [i, x] }.to_h

Answer 3

x = Hash.new{|h, k| h[k] = arr[k]}

Answer 4

%w[one two three four five].map.with_index(1){ |*x| x.reverse }.to_h
Remove (1) if you want to start the index from 0.

Answer 5

Here is a solution making use of Object#tap, to add values to a newly-created hash:
arr = ["one", "two", "three", "four", "five"]
{}.tap do |hsh|
arr.each_with_index { |item, idx| hsh[idx] = item }
end
#=> {0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}

Answer 6

Many good solutions already, just adding a variant (provided you do not have duplicated values):
["one", "two", "three", "four", "five"].map.with_index.to_h.invert
# => {0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}

Answer 7

You could monkey patch Array to provide a new method:
class Array
def to_assoc offset = 0
# needs recent enough ruby version
map.with_index(offset).to_h.invert
end
end
Now you can do:
%w(one two three four).to_assoc(1)
# => {1=>"one", 2=>"two", 3=>"three", 4=>"four"}
This is a common operation I'm doing in Rails apps so I keep this monkey patch around in an initializer.

Answer 8

You should go with the map method, it's better and uses less memory. Another solution is with while loop. Good to know this way too, because often you may need to use the while loop.
At example 2, if you want to take each odd index in the an array as a key in the hash, and each even index as a value in the hash
Example 1:
some_array = ["one", "two", "three", "four", "five"]
def to_hash(arr)
counter = 0
new_hash = Hash.new(0)
while counter < arr.length
new_hash[counter] = arr[counter]
counter += 1
end
return new_hash
end
puts to_hash(arr)
# Output
{0=>"one", 1=>"two", 2=>"three", 3=>"four", 4=>"five"}
Example 2 -
Perhaps after getting data as a string, and you split this string to an array, and now you want to convert to key, value.
some_array = ['KBD', 'King Bedroom', 'QBD', 'Queen Bedroom', 'DBD', 'Double Bedroom', 'SGLB', 'Single Bedroom']
def to_hash(arr)
new_hash = Hash.new(0)
counter = 0
while counter < arr.length
new_hash[arr[counter]] = arr[counter+1]
counter += 2
end
return "#{new_hash}"
end
puts to_key_value_hash(some_array)
# Output
{"KBD"=>"King Bedroom", "QBD"=>"Queen Bedroom", "DBD"=>"Double Bedroom", "SGLB"=>"Single Bedroom"}
Many ways to do this, but just saying not to forget the while loop.