Therefore

A simple wrapper for if conditionals, what each is for while loops.

Just like each, therefore relies on block semantics, so it's essentially an if conditional with a scope, a closure, and the ability to be chained with other methods.

Add this line to your application's Gemfile:

gem 'therefore', '~> 1.0'

And then execute:

$ bundle

Or you can install the gem on its own:

gem install therefore

obj.therefore {...} will invoke the block, yielding obj to it, unless obj is either nil or false. If the block is invoked its result is returned, otherwise obj is returned:

def find_user input: {}
  input[:id].therefore do |user_id|
    User.find user_id
  end
end

find_user input: {id: 1} # => #<User id: 1, ...>
find_user input: {id: nil} # => nil

obj.otherwise {...} behaves symmetrically to therefore: it only invokes the block, again yielding obj, if obj is either false or nil. Again, if the block is invoked its result is returned, otherwise obj is returned. If you chain it with therefore, it can work as an else branch:

def find_user input: {}
  input[:id].therefore do |user_id|
    User.find user_id
  end.otherwise do
    User.default
  end
end

find_user input: {id: 1} # => #<User id: 1, ...>
find_user input: {id: nil} # => #<User default: true, ...>

You can also invoke otherwise with a parameter, in which case it works as an elsif branch:

obj.otherwise(other_obj) do |var|
  ...
end

is equivalent to

obj.otherwise do
  other_obj.therefore do |var|
    ...
  end
end

Both therefore and otherwise can be called without a block, in which case they return an enumerator. If the block would have been invoked the enumerator contains obj, otherwise it is empty:

nil.therefore.to_a # => []
nil.otherwise.to_a # => [nil]
'string'.therefore.to_a # => ['string']
'string'.otherwise.to_a # => []

Therefore loosely follows Semantic Versioning, with a hard guarantee that breaking changes to the public API will always coincide with an increase to the MAJOR number.

Version numbers are in three parts: MAJOR.MINOR.PATCH.

• Breaking changes to the public API increment the MAJOR. There may also be changes that would otherwise increase the MINOR or the PATCH.
• Additions, deprecations, and "big" non breaking changes to the public API increment the MINOR. There may also be changes that would otherwise increase the PATCH.
• Bug fixes and "small" non breaking changes to the public API increment the PATCH.

Notice that any feature deprecated by a minor release can be expected to be removed by the next major release.

Full list of changes in CHANGELOG.md

Bug reports and pull requests are welcome on GitHub at https://github.com/moku-io/therefore.

The gem is available as open source under the terms of the MIT License.