class-constants

In Ruby how does one create a private class constant? (i.e one that is visible inside the class but not outside) class Person SECRET='xxx' # How to make class private?? def show_secret puts "Secret: #{SECRET}" end end Person.new.show_secret puts Person::SECRET # I'd like this to fail You can also change your constant into a class method: def self.secret 'xxx' end private_class_method :secret This makes it accessible within all instances of the class, but not outside. Renato Zannon Starting on ruby 1.9.3, you have the Module#private_constant method, which seems to be exactly what you wanted:

I would like to be able to do something like this: class ThingIDs { const Something = 1; const AnotherThing = 2; } $thing = 'Something'; $id = ThingIDs::$thing; This doesn't work. Is there a straightforward way of doing something equivalent? Note that I'm stuck with the class; it's in a library I can't rewrite. I'm writing code that takes arguments on the command line, and I would really like it to take symbolic names instead of id numbers. Dan Simon $id = constant("ThingIDs::$thing"); http://php.net/manual/en/function.constant.php Use Reflection $r = new ReflectionClass('ThingIDs'); $id = $r-

Suppose you need to define a class which all it does is hold constants. public static final String SOME_CONST = "SOME_VALUE"; What is the preferred way of doing this? Interface Abstract Class Final Class Which one should I use and why? Clarifications to some answers: Enums - I'm not going to use enums, I am not enumerating anything, just collecting some constants which are not related to each other in any way. Interface - I'm not going to set any class as one that implements the interface. Just want to use the interface to call constants like so: ISomeInterface.SOME_CONST . Use a final class.

Python 3.4 introduces a new module enum , which adds an enumerated type to the language. The documentation for enum.Enum provides an example to demonstrate how it can be extended: >>> class Planet(Enum): ... MERCURY = (3.303e+23, 2.4397e6) ... VENUS = (4.869e+24, 6.0518e6) ... EARTH = (5.976e+24, 6.37814e6) ... MARS = (6.421e+23, 3.3972e6) ... JUPITER = (1.9e+27, 7.1492e7) ... SATURN = (5.688e+26, 6.0268e7) ... URANUS = (8.686e+25, 2.5559e7) ... NEPTUNE = (1.024e+26, 2.4746e7) ... def __init__(self, mass, radius): ... self.mass = mass # in kilograms ... self.radius = radius # in meters ...

I am currently trying to dig deeper into the specification of the Java Virtual Machine. I have been reading Inside the JVM book online and there is one confusing abstraction I can't seem to grasp: Constant Pool. here is the excerpt from the book: For each type it loads, a Java virtual machine must store a constant pool. A constant pool is an ordered set of constants used by the type, including literals (string, integer, and floating point constants) and symbolic references to types, fields, and methods. Entries in the constant pool are referenced by index, much like the elements of an array.