Smalltalk and Object Orientation: an Introduction - Free

24.4 Methods
24.4.1 Naming methods
Method names should always start with a lower case letter. If the method name is made up of more than
one element then each eleme nt following the first one, should start with a capital letter. This standard
follows that used for variable names. For example:
account deposit: 100
account printStatement.
If the method is a keyword method containing more than one parameter, then each of the key words
should start with a lower case letter, with each subsequent word starting with a capital letter. For
example:
Dialog request: 'Name' initialAnswer: 'John'
onCancel: [Transcript show: 'Error'].
The naming of methods is extremely important. An appropriate method name will not only make the
code easier to read it will also aid in reuse. Therefore method names should be selected to illustrate the
method’s purpose. In addition, it is common to try to select a name which makes it possible to read an
expression containing the method name in a similar manner to reading a sentence . For example:
statement deposit: 100 on: Date today.
This is actually helped by the ability to spread the arguments amongst the method name.
Methods which return true and false as the result of some test follow a common format throughout
the Smalltalk system. These methods use a verb such as is or has concatenated with whatever is being
tested, for example :
isString
isActive
hasFood
Notice that in the first case the method is testing to see if the receiver is an object of class String.
It therefore uses the name of the class in the method name. In the next two cases some aspect of the
receiver is being tested. For example, the second method may test to see if a process is active or not. In
this case, the value being tested for is used as part of the method name.
24.4.2 General comments about methods
In general it is better to percolate a method up as high as possible in the inheritance hierarchy as long as
it makes sens e. The higher the method is, the more visibility it has to classes in other branches of the
hierarchy, and the more method level reuse you can achieve. You should also consider:
The role of a method. Think carefully about the purpose and placement of methods within a class. Just
as a class should have a specific purpose, at a lower level a method should also have a single
purpose. If a method is used to perform more than one function, then it should be divided into
separate methods. In general terms methods should be no longer than one page of A4. Small but
beautiful methods are desirable.
Code placement within methods. Deciding how to break up the desired functionality into procedural
elements can be difficult in procedural programming languages. In Smalltalk it is made more
difficult by considerations of object encapsulation and reuse. However, there are a number of
questions which you can bear in mind when determining whether your code is correctly placed
within the methods you have defined:
• If a method does not refer to any aspect of the object (e.g. super, self, or instance variables
etc.) what is it doing? Should the method be there?
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