Generate hash for value 1 to 31 with ruby?

How can I generate ha开发者_Go百科sh something like this ?

{1 => 1, 2 => 2, 3 => 3}

from 1 to 31 with loop.

For example:

(1..31).inject({}) { |h, k| h[k] = k; h}

If you want a hash that works for all numbers, you can do it this way:

>> h = Hash.new { |h, k| h[k] = k } #=> {}
>> h[221] #=> 221

def generate_hash r
  Hash[r.zip r]
end

generate_hash (1..31)

Another one-liner:

Hash[(1..31).map {|i| [i,i]}]

Try this

h = Hash.new()
for i in 1..31
    h[i] = i
end

Also, the question did not specify whether the order is important, but if order is important, you might want to consider a different sorting options, as describe here

Sorting Hash of Hashes by value (and return the hash, not an array)

(1..31).inject({}) { |hash, item| hash.merge(item => item) }

Why are you doing this? Are you doing this because there's 31 days in a month?

Anyway:

hash = Hash.new() {|_, key| key if (1..31).include?(key) }
hash[1] # => 1
hash[31] # => 31
hash[32] # => nil

Edit: Now with code golfing from Michael Kohl!

My small contribution:

Hash[1.upto(31).zip 1.upto(31)]

or

Hash[(1.upto 31).zip(1.upto 31)]