Computer Programming with GNU Smalltalk - Free

printString, ' years old.'; cr.
]
]
> aHuman [
^age > aHuman getAge
]
< aHuman [
^age < aHuman getAge
]
= aHuman [
^age = aHuman getAge
]
| me myBrother |
me := Human new.
me setName: 'Canol Gökel'.
me setAge: 24.
myBrother := Human new.
myBrother setName: 'Gürol Gökel'.
myBrother setAge: 27.
me introduceYourself.
myBrother introduceYourself.
(me < myBrother) printNl.
Hello, my name is Canol Gökel and I'm 24 years old.
Hello, my name is Gürol Gökel and I'm 27 years old.
true
Objects, Messages and Classes: Part II 69
Our Human class is pretty simple. It has two instance variables named name and age. After defining the
accessors (setName:, getName etc.) we defined a method named introduceYourself. When a
Human object is sent this message, it introduces itself by telling some information about itself. We have
also written methods to compare two Human's age. If a comparison is wanted to be done among two
Human objects, you can use >, < or = binary messages. Notice that we have used the instance variable
age for the receiver and sent the getAge message to the argument object to reach the ages of them
which are integer numbers. The comparison methods are already defined for Integer objects so we
don't have to go deeper.
This implementation is pretty simple. Suppose that we needed to add a few more details to this class.
We can modify the above code directly but there will be times that we don't want to modify the
original code. For example, maybe more than one program is sharing the code and only one of them is