Ruby by Example

#16 Adding Commas to Numbers (commify.rb)

A standard way of formatting numbers is to present them with commas (or some other delimiter) separating each group of thousands. Our next script does that by adding a method called commify to all numbers. You might think that we could do this by opening the Integer class and adding a new method to it, as we did in power_of.rb. This is certainly a reasonable approach, except that we may want to use commify on floating-point numbers as well. What’s the solution?

Inheritance

The answer deals with an object-oriented concept called inheritance. We discussed this earlier in Chapter 3 when we added methods to the Object class. Inheritance is what allows all other classes to use methods of the Object class, because ...