do.rb

class TrueClass
  def do(_if: ->{}, _else: ->{})
    _if.call
    self
  end
end

class FalseClass
  def do(_if: ->{}, _else: ->{})
    _else.call
    self
  end
end
  

then_else.rb

class TrueClass
  def then
    yield
    self
  end

  def else
    self
  end
end

class FalseClass
  def then
    self
  end

  def else
    yield
    self
  end
end
  

Looking at readability:

    model.persist.then do
      # what to do if
      # result was positive
      # maybe add notes or send an email
    end.else do
      # it didn't work out. Handle that.
    end

In terms of readability... I think it's better than a ternary, but the end.else... I wish it could have just been else. I guess using curlies would make it better.

    model.persist.then {
      # what to do if
      # result was positive
      # maybe add notes or send an email
    }.else do
      # what to do if there was some problem
    }

for multiline, how is that any more readable than

if model.persist
  # what to do if
  # result was positive
  # maybe add notes or send an email
else
  # it didn't work out. Handle that.
end

? :)

What do you think about 'otherwise' as an alias for else?

find_user_by_email( 'jw@mustmodify.com' ).otherwise do
  puts "Sorry, no such user."
end

maybe I'm overthinking.

It isn't any more readable. But it's more OO or, as you said, smalltalky, which makes me happy.

https://github.com/mustmodify/then_else.rb