Class Level Variables in Perl
The Perl programming language supports object-oriented programming, which deals with interaction between objects. Objects are instances of classes, which are collections of related functions and values. Class-level variables, also known as class attributes, are variables that can be accessed by any object within a class. On the other hand, instance level variables can only be accessed by one instance, or object. Class-level variables have several advantages, disadvantages and uses that you should know.
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Advantages of Class Variables
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Class-level variables offer several advantages. A class-level variable can be accessed by every object within the class. This is convenient for data that is universal across the class. Class-level variables also simplify certain aspects of coding, since objects do not require an elaborate system to allow data exchange.
Disadvantages of Class Variables
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Class-level variables have some drawbacks. Since the class-level variables are shared by all objects in the class, the variable has no access control. Any object can modify the variable, which is inappropriate for data that represents a value unique to a class instance.
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Accessor Methods
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Class attributes should not be accessed directly but should instead be accessed through accessor methods. Accessor methods get and set class attributes. Using accessor methods is a good practice of object-oriented programming, since it separates the interface (the functions and data types visible to clients) and the implementation (the nuts and bolts code).
Examples of Use
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Class-level variables can be used in many applications:
Storing a list of objects;
Tracking what object was last accessed, or tracking the most accessed object;
Sharing universal data between objects;
Storing a reference to a file that all objects can access, such as a logfile.
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