hierarchy

I'm trying to understand how a class defined in a module knows the module's constants. Here's an example of what I mean: module Car class Wheel end class Seat p Wheel # Car::Wheel end end I know it's obvious, but since Wheel is nowhere in Seat's hierarchy, I don't understand how it can have access to it. If you reference a class constant, Ruby will look for it first in the same module, and then on the root if it's not found there. So, since both Seat and Wheel are in the Car module, if you look for Wheel , it will first look for Car::Wheel , and then for ::Wheel . Since Car::Wheel exists, you

Given an EmployeeId, how can I construct a Linq to Sql query to find all of the ancestors of the employee? Each EmployeeId has an associated SupervisorId (see below). For example, a query of the ancestors for EmployeeId 6 (Frank Black) should return Jane Doe, Bob Smith, Joe Bloggs, and Head Honcho. If necessary, I can cache the list of all employees to improve performance. UPDATE: I've created the following crude method to accomplish the task. It traverses the employee.Supervisor relationship all the way to the root node. However, this will issue one database call for each employee. Anyone

I'm implementing value types which represents a distance (or length). There's an enum that represents the different units of measure, eg: public enum DistanceUnit { Millimeter, Centimeter, Meter, Kilometer, Inch, Foot, Yard, Mile }; These measurements fall into one of two systems - either metric or imperial. Since enum doesn't support hierachies, what's the best pattern for representing this hierarchy? Is it to use bit flags? Or use two seperate enums along with some methods to correlate them? Or to declare static members instead of enums? Give me some advice... how would you implement this?

I'm already familiar with Linq but have little understanding of extension methods I'm hoping someone can help me out. So I have this hierarchical collection pseudo code ie: class Product prop name prop type prop id prop List<Product> children And I have a list of products List products. Is there any way I can look for product in this collection by the id with a extension method ? In other words I need one item somewhere within the hierarchy. Here is a generic solution that will short-circuit traversal of the hierarchy once a match is found. public static class MyExtensions { public static T

The parentViewController property of UIViewController is readonly, but I am nesting custom view controllers and would like to use this property. However, since it is readonly, and I found no other way to set this property, my quesion is: how do I set it? Obviously, UINavigationController can set the property somehow in -pushViewController, and so can -presentModalViewController, so it must be possible. I am aware that I can just add my own UIViewController property, but I'm sure that parentViewController is, in principle, the correct property. However, since it is readonly, and I found no

I'd love to hear what advice the Clojure gurus here have about managing state in hierarchies. I find I'm often using {:structures {:like {:this {:with {:many 'levels}} } } } and if I want to track changes in state at multiple levels, by throwing atoms around values (atom {:like (atom 'this)} ) , I find myself thinking this must be wrong. Is it generally better to use just one atom at the top level, and have none as values in a map ? Don't use nested atoms in a data structure if at all possible. The main reason is that immutability is your friend. Clojure is a functional language that thrives