Explain Ruby code

What this Ruby sample shows

mixins

include Greeting adds greet to every Member. include Comparable adds comparison methods such as <, >, == and between?, all built on the <=> method the class defines.

blocks

{ |m| m.points > 20 } is a block passed to select, which keeps the members the block returns true for.

symbols

:name and :points are symbols. map(&:name) turns the symbol into a block that calls name on each member.

metaprogramming

attr_reader :name, :points writes the two reader methods for you when the class is defined, so points works without a def points.

Good to know

• <=> returns -1, 0 or 1. max and sort only need that method, so the script prints Hi, I'm Ben, then Ana, Ben, then ["Cy", "Ana", "Ben"].
• greet calls name without self., because a method from a module runs on the object it was mixed into.

Watch out: Comparable also defines == from <=>, so two different members with the same points count as equal: Member.new("Al", 5) == Member.new("Bo", 5) is true.