How to Change Hash Values

How to change Hash values?

my_hash.each { |k, v| my_hash[k] = v.upcase } 

or, if you'd prefer to do it non-destructively, and return a new hash instead of modifying my_hash:

a_new_hash = my_hash.inject({}) { |h, (k, v)| h[k] = v.upcase; h } 

This last version has the added benefit that you could transform the keys too.

How can I replace a single Hash Value in Ruby by using its number

You can do hashOne[hashOne.keys[3]] = 'rubypro'. Also I remember reading that Hashes in ruby are ordered but I'm not entirely sure. (Be careful with using indices because they may not be ordered in other languages) I would ensure that the keys are always returned in the same order before trying to assign a key with an index.

If you really wanted to use an index, I'd recommend using an array because that's not the purpose of a key/value hash.

Ruby: What is the easiest method to update Hash values?

You can use update (alias of merge!) to update each value using a block:

hash.update(hash) { |key, value| value * 2 }

Note that we're effectively merging hash with itself. This is needed because Ruby will call the block to resolve the merge for any keys that collide, setting the value with the return value of the block.

Change sha1 hash of files

Yes.

Either:

• Change the content of the file so the two files are identical or
• Find another set of data (you'll probably have to brute force search this so it would take a lot of computing power) which happens to hash to the same value

You can't change the hash without changing the content of the file. The hash is just what you get after doing some calculations on the content of the file.

How to change hash key from array of hashes in ruby?

You can also use .map and .tap like this

data.map do |h|
 h.tap { |m_h| m_h["user_ids"]= m_h["user_ids"].split(',').first(5)}
end

Crystal - How to recursively change Hash values and save each change to new Hash

Crystal v0.25.0 implements JSON::Any and YAML::Any without recursive aliases. With that change:

require "json"

hash = JSON.parse(%(
  {"foo": {"bar": 1, "baz": 2}, "bla": [1,2,3]}
))

def changer(any : JSON::Any)
  result = [JSON::Any.new("*")]
  if (hash = any.as_h?)
    hash.each do |key, value|
      changer(value).each do |s|
        result << JSON::Any.new(hash.merge({key => s}))
      end
    end
  end
  result
end

puts changer(hash).join("\n")

*
{"foo" => "*", "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => "*", "baz" => 2_i64}, "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => 1_i64, "baz" => "*"}, "bla" => [1_i64, 2_i64, 3_i64]}
{"foo" => {"bar" => 1_i64, "baz" => 2_i64}, "bla" => "*"}

How to change hash return format for Ruby

You have an Hash with Symbol keys:

h = {"description": "Hello", "id": "H"}

Consider this:

({"description": "Hello", "id": "H"}) == ({"description"=> "Hello", "id"=> "H"})
#=> false

({"description": "Hello", "id": "H"}) == ({description: "Hello", id: "H"})
#=> true

Ruby just removes " when printing:

p ({"description":"Hello","id":"H"})
#=> {:description=>"Hello", :id=>"H"}

---

If you want to convert keys to String, you could use pure Ruby Hash#transform_keys (or the bang version transform_keys!):

h.transform_keys &:to_s
#=> {"description"=>"Hello", "id"=>"H"}

---

If a json is what you are looking for, do:

require 'json'

puts h.to_json
#=> {"description":"Hello","id":"H"}

---

Consider also that:

h.to_json.class #=> String
h.class #=> Hash

---

---

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