Created August 8, 2009
Last updated August 8, 2009
Instance-scope operation and Class-scope operation
In the Class diaglam, we can define operations in the class. Operations are classifed into 2 groups whether it is instance-scope.
One is an instance-scope operation,and the other is a class-scope operation.
In this page, I will explain the feature and the use of the instance-scope operation and the class-scope operation
1.
Attention:To understanding this pase , you shoud understand "
Instance-scope attribute and Class-scope attribute".
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Note.
1:If beginners of the object-oriented program a java application, usually all method ( operation ) is static ( Formerly, I was so ).
If you are so , I want you to read this page , notice the mistake.
Instance-scope operations are defined at setting and getting the value of Instance-scope attributes.
Please read "2.When to define an instance-scope operation?".
I define an instance-scope operation at the following.
- When I want to setting 2 or more instance-scope attributes at the same time , checking the parameter ( range check and so on) , locking the mutex ( thread safe ) and defining the read-only attribute , or when I assume to modifying like these.
- When I want to processing some datas based on present datas.
For example , in java , there are java.io.File.Delete() , java.security.MessageDigest.digest().
In Excel VBA , there are Activate() , Close() , and PrintOut() methods of Workbook class, Execute() method of CommandbarButton class.
Of course , there are more methods.
Class-scope operations are defined at setting and getting the value of class-scope attributes.
In the class diaglam , class-scope operations are underlined 1.
Please read "4.When to define a class-scope operation?".
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Note.
1:The class-scope attribute and operation are underlined. That is written in the UML Superstructure Specification v2.0 "7.3.19 Feature (from Kernel)"(p67).
I define a class-scope operation at the following.
- When I want to setting 2 or more class-scope attributes at the same time , checking the parameter and so on.
(This is the same as an instance-scope operation.)
- When I want to defining an operation of the "utility class".
The utility class is composed only functions and constants. For examle , there are java.lang.Math class ( Java ) , DateTime module ( VBA ).
An utility class is not capable of creating instances.
In the class diaglam, an utility class is written "<<utility>>" keyword on the class name.
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