Computer Programming with GNU Smalltalk - Free

Objects, Messages and Classes: Part II 61
They are only for documentation purposes and appear on IDEs we use for explaining what a class or
method does so that we can get an idea of what it does without looking at its code which would took
much longer and be harder. They do not affect the execution of the program, so, we can omit them.
And the time comes to defining the class and instance methods. We first created a class method:
SubclassName class >> aClassMethod: aParameter [
"Comment to describe this class method"
]
| localVariable1 localVariable2 |
...
^objectToReturn
We again have a header part and a body part here. The header of the class definition is:
SubclassName class >> aClassMethod: aParameter
SubclassName class >> part of this header tells us that we are going to create a method for the
class, not for the instances of the class. If we'd omitted this part then the method would be a part for the
instances of this class. After this part we specify our method's message. The selector of this message is
aClassMethod:. It takes a parameter named aParameter. Parameters are the names given to the
argument names when they are used in the header of methods, so these words are actually not that
different from arguments and sometimes used in exchange. We may use the parameter names inside our
method to refer to the argument passed to the method.
After specifying the selector we opened the bracket to define the method content which is called the
body of the method:
[
]
"Comment to describe this class method"
| localVariable1 localVariable2 |
...
^objectToReturn
The content of a method can be made of a comment, a category, some local variables and the
expressions to execute which are shown as three dots. After writing a comment with: