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Saving Star: Family Tree Exercise

Peter Degen-Portnoy

August 5, 2012

To Install

> git clone git://github.com/PeterDP/family_tree.git
> cd family_tree
> bundle install
> rake db:setup

To Verify Installation

> rake spec

To Run

> rails s

Running at default location: localhost:3000

Notes

  • Tested in Chrome 20.0.1132.57 and Firefox 13.0.1 in OS/X
  • A family has to start somewhere. Siblings are defined by having the same parent (at least one), so, at the top of the family tree, which are the root node grandparents, those grandparents can't have any siblings
  • To create a new person, use the "New Person" link at the bottom of the "People in the Family" index page. Most everything else can be done from the person show page.
  • Marriage is between two people, no checking is performed. Polygamy is not allowed.
  • Divorce is not implemented, but would be supported. People can end their marriage, marry to another, and produce offspring
  • I chose to hide the edit person functionality at this point.
  • The foremost consideration was modeling the relationships between people, which seems to be ideally modeled in a tree relationship Therefore, I explored gems such as acts_as_tree and ancestry. However, a fundamental assumption in these models is that there is one root node. While it would have been possible to create each person as a root node, then the offspring as children nodes, modeling marriage and tracking single parents, married parents and divorces/remarriages would have driven significant complexity. Therefore, I decided that there would be two types of relationships, a Couple and Offspring. With this model, the only complexity is that when a person who is in a Couple relationship has an offspring, the spouse is also identified as a parent of the offspring.
    This provides the relatively easy definition of a Sibling being anyone who has at least one shared parent.
  • The part of this exercise with which I am not satisfied is how relationships are created. The Person model is fat so that a person bears the responsibility of getting married and having a child, both of which create the necessary Relationship object. However, it may have been cleaner to do something like Couple.create(@partner_a, @partner_b). It seemed just as valid to say @partner_a.marry(@partner_b). That Person-centric perspective made more sense when having offspring. Offspring.create(@parent,@child) was decidedly less satisfying than @parent.has_child('child_name', birthdate). So, I decided to stay with a domain model that seemed more logical to me than stick with the canonical usage of the Relationship hierarchy and RESTful routes for creating relationships

Known Issues

  • Through the "parent" link, you can create more than two parents, though that's not possible when Person A marries Person B and has a child
  • The click event for the class "create_person" was occasionally not being registered. The behavior was intermittent and resulted in the Create Person, Create Parent and Create Child modal dialog not being used and the default HTML page to be displayed instead.
    Haven't seen that in a while, though.