1. Ruby Classes

2. Classes
Classes in Ruby are similar to classes in other familiar languages with some interesting differences
We will see how to write classes and different related features

3. Remember convention @ - instance variable @@ - class variable
No symbol in front of it – local variable
We will discuss this more soon

4. Initializing
Initialize is a special method
always private

5. Access Control private, public, protected like other languages
Except private is really private
only accessible on self, not even on other objects of same class
You can’t call private explicitly using a receiver, it can only be called on an implicitly receiver
There are some tricky ways to get around this…
Default is public
You can specify access control one of two ways

6. Especially useful when you
Access Control…
Especially useful when you
want to make some
attributes protected

7. Attributes – readers :name returns a Symbol object
: represents name of a variable while
variable name represents the
value of the variable
Creates year method and
@year instance variable

8. Attributes - Writer OR

9. What’s wrong with this code?
We’re missing
Coming from other languages we tend to do this for a while

10. A little gotcha
The return value from assignment method is ignored

11. Inheritance You use < to express inheritance
Super call’s respective base method

12. Inheritance… Ruby supports Single Inheritance like Java/C#
But how about multiple inheritance
No and Yes
Not supported, but
There is a very powerful Mixin – more about this later

13. Classes never closed
You can add methods to any class you like

14. method_missing
You can dynamically figure out what to do when methods are called
Ruby calls method_missing when it can’t hande a method
After adding
method_missing