Class and Instance Methods in Ruby

Class and Instance Methods in Ruby

The other day I was explaining the difference between class and instance methods to a friend and I realized that I should probably write up a post. I figured since I’m on a plane headed back home, now was as good of time as ever. If you want a little history, you can read about the difference between class and instance variables . One Line Summary Class methods are methods that are called on a class and instance methods are methods that are called on an instance of a class. Here is a quick example and then we’ll go into a bit more detail. class Foo def self.bar puts 'class method' end def baz puts 'instance method' end end Foo.bar # => "class method" Foo.baz # => NoMethodError: undefined method ‘baz’ for Foo:Class Foo.new.baz # => instance method Foo.new.bar # => NoMethodError: undefined method ‘bar’ for #<Foo:0x1e820> See the difference? bar is a class method , so calling...

Full article: http://www.railstips.org/blog/archives/2009/05/11/class-a...