Conditional Examples in Ruby

pattern-matching.rb

# This is an example using Eventide's message handling DSL for declaring different
# handler methods based on message type
class SomeHandler
  include Messaging::Handle
  
  handle SomeMessage do |some_msg|
    # ...
  end

  handle OtherMessage do |other_msg|
    # ...
  end
end

return-value-destructuring.rb

# This is a pattern @sbellware taught me (and possibly invented). When a method call
# can have ancillary return values, the method can then accept an `include' keyword
# argument (optionally) that specifies additional return values. For intsance, given
# a store that fetches entities, and *also* caches them behind the scenes, we can
# tell a store to fetch an entity *and* return the timestamp for when the entity
# was cached.

# Normal fetch call, only returns an entity
entity = store.fetch(id)

# Include the cache record timestamp in the return value
entity, cached_time = store.fetch(id, include: :cached_time)

traditional-query.rb

# Traditional, perform a query, make a decision based on the result.
# Note that in practice, the query *and* the decision should always go
# in the same class. The danger with result objects is that they allow
# query results to break encapsulation
class SomeClass
  def initializer(id)
    @id = id
  end
  
  def some_method
    entity = SomeRepository.get(@id)
    
    if entity.nil?
      # ...
    else
      # ...
    end
  end
end