Null Object Design Pattern
The Null Object Design Pattern is a behavioral design pattern that provides a consistent approach for handling null or non-existing objects. It is especially beneficial when you want to avoid explicit null checks and instead offer a default behavior for objects that might not exist.
Problem:
In object-oriented programming, encountering null references is a common issue, especially when objects are returned as null or passed as arguments.
Solution:
Using conditional statements can help address this problem, but in a real-world project with thousands of classes and functions, managing null checks everywhere becomes challenging.
To mitigate this situation, we can create a
NullObject class that provides default behavior.
NullObject -- provides an interface identical to AbstractObject's so that a null object can be substituted for a real object
- implements its interface to do nothing. What exactly it means to do nothing depends on what sort of behavior Client is expecting
- when there is more than one way to do nothing, more than one NullObject class may be required
Key Points:
- The Null Object class is typically implemented as a Singleton. Since a null object usually lacks any state, its state remains constant, making multiple instances identical. Instead of creating several identical instances, the system can efficiently utilize a single instance.