Computer Programming with GNU Smalltalk - Free

]
]
'Woof!' printNl.
Animal subclass: Cat [
]
makeNoise [
"An instance method to get the cat's noise."
]
'Miaow!' printNl.
dog := Dog new.
Animal setAnimalNumber: 1.
dog setName: 'Karabash'.
dog getName printNl.
dog makeNoise.
cat := Cat new.
Animal setAnimalNumber: 2.
cat setName: 'Minnosh'.
cat getName printNl.
cat makeNoise.
'Karabash'
'Woof!'
'Minnosh'
'Miaow!'
2
Objects, Messages and Classes: Part II 65
Now we will investigate this program line by line. We first create our class by inheriting an object
named Object which is a special object: ancestor of all classes we will create. It comes with some
useful methods predefined for us like new:
Object subclass: Animal [
...
]
Next thing we do is to declare an instance variable named name and a class variable named
animalNumber. We will give a name to our animals and keep the number of the animals we created in
the class variable:
| name |
animalNumber := 0.