Converting String from Snake_Case to Camelcase in Ruby

Converting string from snake_case to CamelCase in Ruby

If you're using Rails, String#camelize is what you're looking for.

  "active_record".camelize                # => "ActiveRecord"
  "active_record".camelize(:lower)        # => "activeRecord"

If you want to get an actual class, you should use String#constantize on top of that.

"app_user".camelize.constantize

Converting camel case to underscore case in ruby

Rails' ActiveSupport
adds underscore to the String using the following:

class String
  def underscore
    self.gsub(/::/, '/').
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
    gsub(/([a-z\d])([A-Z])/,'\1_\2').
    tr("-", "_").
    downcase
  end
end

Then you can do fun stuff:

"CamelCase".underscore
=> "camel_case"

Converting snake case to normal sentence in Ruby

humanize is your thing:

[4] pry(main)> "hello_world".humanize
"Hello world"

Julia implementation for converting string to snake_case/CamelCase

This doesn't use "reserved words" as mentioned in the question, but instead assumes that a series of upper case letters (along with preceding numbers if any, for eg. "30MW") is supposed to be a word of its own; while also ensuring that "Price" in "30MWPrice" is seen as a separate word.

function snake_case(camelstring::S) where S<:AbstractString

  wordpat = r"
  ^[a-z]+ |                  #match initial lower case part
  [A-Z][a-z]+ |              #match Words Like This
  \d*([A-Z](?=[A-Z]|$))+ |   #match ABBREV 30MW 
  \d+                        #match 1234 (numbers without units)
  "x

  smartlower(word) = any(islowercase, word) ? lowercase(word) : word
  words = [smartlower(m.match) for m in eachmatch(wordpat, camelstring)]

  join(words, "_")
end

using Test

function runtests()
  @test snake_case("askBest30MWPrice") == "ask_best_30MW_price"
  @test snake_case("welcomeToAIOverlords") == "welcome_to_AI_overlords"
  @test snake_case("queryInterface") == "query_interface"
  @test snake_case("tst") == "tst"
  @test snake_case("1234") == "1234"
  @test snake_case("column12Value") == "column_12_value"
  @test snake_case("readTOC") == "read_TOC"
end

(Probably Unimportant) Side Note: You can replace [a-z] with [[:lower:]] and [A-Z] with [[:upper:]] above to make it work for some more languages, for eg. snake_case("helloΩorld") will then return "hello_ωorld". However (like with anything Unicode), there are nuances - for eg., my language (Tamil) doesn't have letter cases, so its letters fall outside both [:lower:] and [:upper:].

A proper Unicode solution using \p{Lo}, [:digit:], and whatever else, is left as an exercise to the reader.

How to convert snake case to dash case in Rails

dasherize right there on the same page

"hello_world".dasherize # => 'hello-world'

Converting nested hash keys from CamelCase to snake_case in Ruby

You need to treat Array and Hash separately. And, if you're in Rails, you can use underscore instead of your homebrew to_snake_case. First a little helper to reduce the noise:

def underscore_key(k)
  k.to_s.underscore.to_sym
  # Or, if you're not in Rails:
  # to_snake_case(k.to_s).to_sym
end

If your Hashes will have keys that aren't Symbols or Strings then you can modify underscore_key appropriately.

If you have an Array, then you just want to recursively apply convert_hash_keys to each element of the Array; if you have a Hash, you want to fix the keys with underscore_key and apply convert_hash_keys to each of the values; if you have something else then you want to pass it through untouched:

def convert_hash_keys(value)
  case value
    when Array
      value.map { |v| convert_hash_keys(v) }
      # or `value.map(&method(:convert_hash_keys))`
    when Hash
      Hash[value.map { |k, v| [underscore_key(k), convert_hash_keys(v)] }]
    else
      value
   end
end

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