後置 while にする?

gistfile1.rb

def generate_name
  begin
    name = Digit.generate(6)
  end while Image.exists?(name: name)
  name
end

def generate_name
  loop do
    name = Digit.generate(6)
    return name unless Image.exists?(name: name)
  end
end

def _generate_name; loop { yield(Digit.generate(6)) }; end

def generate_name
  enum_for(:_generate_name).lazy.select{|name| !Image.exists?(name: name) }.first
end