Class Extension: How to Override or Add New Functionality to Existing Script Include?
Code
The above code demonstrates the concept of class extension in ServiceNow by extending an existing class (E.g. MultipartHelper) to add custom functionality and override methods. Below is an explanation of the code and its benefits:
Code Explanation
- Class Creation and Extension:
- The Class.create() method defines a new class called MultipartHelperExtended.
- The Object.extendsObject() method extends the MultipartHelper class, allowing MultipartHelperExtended to inherit all its properties and methods.
- Adding a New Method (myBaseFunction):
- This method demonstrates how to call a base class’s method (getContentType) directly from the extended class.
- The parent method is accessed using:
MultipartHelper.prototype.getContentType.call(this);
- Adding Another Method (myOverrideFunction):
- This method calls the overridden version of getContentType within the extended class itself.
- The this.getContentType() call executes the overridden method defined in the extended class.
- Overriding a Base Class Method (getContentType):
- The getContentType method is redefined to include custom logic.
- Instead of directly using the parent class's logic, it implements its behavior and logs the action.
Benefits of This Approach
- Code Reusability:
- By extending the base class, the developer avoids duplicating code and directly inherits the base functionality.
- Customization:
- The extended class can modify or override the behavior of the parent class to meet specific requirements, as shown with the overridden getContentType method.
- Modular Design:
- The code is modular, making it easier to maintain and extend further. Each class has a clear separation of concerns.
- Backward Compatibility:
- The original functionality of Script Include (MultipartHelper) remains intact. Any code dependent on it will not break.
Use Cases:
Imagine you are working on a ServiceNow application where Script Include is protected. You want to:
- Add custom processing logic for specific functionality.
- Avoid altering the core class to prevent unintended side effects.
Using this, you can implement your custom logic while preserving the base functionality.
Example Usage
Here’s how the class can be used in a script:
Output Logs
Key Points
- Extending classes allows for easy customization without altering the base class.
- Always use
BaseClassName.prototype.methodName.call(this) to call parent methods in ServiceNow safely.
- Override base methods to provide custom functionality specific to your use case.
- You can use proper logging to make debugging easier.
This approach is a best practice for building scalable and maintainable ServiceNow solutions.
#ScriptInclude #ServiceNow #OOPs
